diff --git a/skops/card/_model_card.py b/skops/card/_model_card.py
index 15a8fe04..5d9942f5 100644
--- a/skops/card/_model_card.py
+++ b/skops/card/_model_card.py
@@ -380,8 +380,18 @@ class Card:
         ``Path``/``str`` of the model or the actual model instance that will be
         documented. If a ``Path`` or ``str`` is provided, model will be loaded.
 
-    model_diagram: bool, default=True
-        Set to True if model diagram should be plotted in the card.
+    model_diagram: bool or "auto" or str, default="auto"
+        If using the skops template, setting this to ``True`` or ``"auto"`` will
+        add the model diagram, as generated by sckit-learn, to the default
+        section, i.e "Model description/Training Procedure/Model Plot". Passing
+        a string to ``model_diagram`` will instead use that string as the
+        section name for the diagram. Set to ``False`` to not include the model
+        diagram.
+
+        If using a non-skops template, passing ``"auto"`` won't add the model
+        diagram because there is no pre-defined section to put it. The model
+        diagram can, however, always be added later using
+        :meth:`Card.add_model_plot`.
 
     metadata: ModelCardData, optional
         :class:`huggingface_hub.ModelCardData` object. The contents of this
@@ -481,13 +491,12 @@ class Card:
     def __init__(
         self,
         model,
-        model_diagram: bool = True,
+        model_diagram: bool | Literal["auto"] | str = "auto",
         metadata: ModelCardData | None = None,
         template: Literal["skops"] | dict[str, str] | None = "skops",
         trusted: bool = False,
     ) -> None:
         self.model = model
-        self.model_diagram = model_diagram
         self.metadata = metadata or ModelCardData()
         self.template = template
         self.trusted = trusted
@@ -495,13 +504,23 @@ def __init__(
         self._data: dict[str, Section] = {}
         self._metrics: dict[str, str | float | int] = {}
 
-        self._populate_template()
+        self._populate_template(model_diagram=model_diagram)
 
-    def _populate_template(self):
-        """If initialized with a template, use it to populate the card."""
-        if not self.template:
-            return
+    def _populate_template(self, model_diagram: bool | Literal["auto"] | str):
+        """If initialized with a template, use it to populate the card.
+
+        Parameters
+        ----------
+        model_diagram: bool or "auto" or str
+            If using the default template, ``"auto"`` and ``True`` will add the
+            diagram in its default section. If using a custom template,
+            ``"auto"`` will not add the diagram, and passing ``True`` will
+            result in an error. For either, passing ``False`` will result in the
+            model diagram being omitted, and passing a string (other than
+            ``"auto"``) will put the model diagram into a section corresponding
+            to that string.
 
+        """
         if isinstance(self.template, str) and (self.template not in VALID_TEMPLATES):
             valid_templates = ", ".join(f"'{val}'" for val in sorted(VALID_TEMPLATES))
             msg = (
@@ -510,15 +529,29 @@ def _populate_template(self):
             )
             raise ValueError(msg)
 
+        # default template
         if self.template == Templates.skops.value:
             self.add(**SKOPS_TEMPLATE)
             # for the skops template, automatically add some default sections
-            self.add_model_plot()
             self.add_hyperparams()
             self.add_get_started_code()
-        elif isinstance(self.template, Mapping):
+
+            if (model_diagram is True) or (model_diagram == "auto"):
+                self.add_model_plot()
+            elif isinstance(model_diagram, str):
+                self.add_model_plot(section=model_diagram)
+            return
+
+        # non-default template
+        if isinstance(self.template, Mapping):
             self.add(**self.template)
 
+        if isinstance(model_diagram, str) and (model_diagram != "auto"):
+            self.add_model_plot(section=model_diagram)
+        elif model_diagram is True:
+            # will trigger an error
+            self.add_model_plot()
+
     def get_model(self) -> Any:
         """Returns sklearn estimator object.
 
@@ -789,9 +822,6 @@ def add_model_plot(
         self : object
             Card object.
         """
-        if not self.model_diagram:
-            return self
-
         if section is None:
             if self.template == Templates.skops.value:
                 section = "Model description/Training Procedure/Model Plot"
diff --git a/skops/card/tests/test_card.py b/skops/card/tests/test_card.py
index 0a97a303..f9d8e0d8 100644
--- a/skops/card/tests/test_card.py
+++ b/skops/card/tests/test_card.py
@@ -177,6 +177,26 @@ def test_model_diagram_false(self):
         ).content
         assert result == "The model plot is below."
 
+    def test_model_diagram_str(self):
+        # if passing a str, use that as the section name
+        model = fit_model()
+        other_section_name = "Here is the model diagram"
+        model_card = Card(model, model_diagram=other_section_name)
+
+        # first check that default section only contains placeholder
+        result = model_card.select(
+            "Model description/Training Procedure/Model Plot"
+        ).format()
+        assert result == "The model plot is below."
+
+        # now check that the actual model diagram is in the other section
+        result = model_card.select(other_section_name).format()
+        assert result.startswith("The model plot is below.\n\n<style>#sk-")
+        assert "<style>" in result
+        assert result.endswith(
+            "<pre>LinearRegression()</pre></div></div></div></div></div>"
+        )
+
     def test_other_section(self, model_card):
         model_card.add_model_plot(section="Other section")
         result = model_card.select("Other section").content
@@ -204,6 +224,47 @@ def test_custom_template_no_section_raises(self, template):
         with pytest.raises(ValueError, match=msg):
             model_card.add_model_plot()
 
+    @pytest.mark.parametrize("template", CUSTOM_TEMPLATES)
+    def test_custom_template_init_str_works(self, template):
+        model = fit_model()
+        section_name = "Here is the model diagram"
+        model_card = Card(model, template=template, model_diagram=section_name)
+
+        result = model_card.select(section_name).format()
+        assert result.startswith("<style>#sk-")
+        assert "<style>" in result
+        assert result.endswith(
+            "<pre>LinearRegression()</pre></div></div></div></div></div>"
+        )
+
+    def test_default_template_and_model_diagram_true(self, model_card):
+        # setting model_diagram=True should not change anything vs auto with the
+        # default template
+        model = fit_model()
+        model_card = Card(model, model_diagram=True)
+        result = model_card.select(
+            "Model description/Training Procedure/Model Plot"
+        ).content
+        # don't compare whole text, as it's quite long and non-deterministic
+        assert result.startswith("The model plot is below.\n\n<style>#sk-")
+        assert "<style>" in result
+        assert result.endswith(
+            "<pre>LinearRegression()</pre></div></div></div></div></div>"
+        )
+
+    @pytest.mark.parametrize("template", CUSTOM_TEMPLATES)
+    def test_custom_template_and_model_diagram_true(self, model_card, template):
+        # in contrast to the previous test, when setting model_diagram=True but
+        # using a custom template, we expect an error during initialization of
+        # the model cord
+        model = fit_model()
+        msg = (
+            "You are trying to add a model plot but you're using a custom template, "
+            "please pass the 'section' argument to determine where to put the content"
+        )
+        with pytest.raises(ValueError, match=msg):
+            Card(model, template=template, model_diagram=True)
+
     def test_add_twice(self, model_card):
         # it's possible to add the section twice, even if it doesn't make a lot
         # of sense