diff --git a/slack_sdk/models/blocks/blocks.py b/slack_sdk/models/blocks/blocks.py
index db4de1f3a..46ed040a2 100644
--- a/slack_sdk/models/blocks/blocks.py
+++ b/slack_sdk/models/blocks/blocks.py
@@ -949,8 +949,8 @@ def __init__(
         self,
         *,
         block_id: Optional[str] = None,
-        hero_image: Optional[str] = None,
-        icon: Optional[str] = None,
+        hero_image: Optional[Union[dict, ImageElement]] = None,
+        icon: Optional[Union[dict, ImageElement]] = None,
         title: Optional[Union[str, dict, TextObject]] = None,
         subtitle: Optional[Union[str, dict, TextObject]] = None,
         body: Optional[Union[str, dict, TextObject]] = None,
@@ -962,8 +962,10 @@ def __init__(
 
         Args:
             block_id: A unique identifier for a block. If not specified, a block_id will be generated.
-            hero_image: Link to the top image used on the card.
-            icon: Link to the small image used next to the card's title and subtitle.
+            hero_image: Link to the top image used on the card. Max length 3000 characters.
+                The alt_text property has a max length of 2000 characters.
+            icon: Link to the small image used next to the card's title and subtitle. Max length
+                3000 characters. The alt_text property has a max length of 2000 characters.
             title: Title of the card. 150 characters max.
             subtitle: Subtitle of the card. 150 characters max.
             body: Content of the card. 200 characters max.
diff --git a/tests/slack_sdk/models/test_blocks.py b/tests/slack_sdk/models/test_blocks.py
index fc9ff3266..ba0d378b1 100644
--- a/tests/slack_sdk/models/test_blocks.py
+++ b/tests/slack_sdk/models/test_blocks.py
@@ -39,7 +39,7 @@
     VideoBlock,
 )
 from slack_sdk.models.blocks.basic_components import FeedbackButtonObject, SlackFile
-from slack_sdk.models.blocks.block_elements import FeedbackButtonsElement, IconButtonElement
+from slack_sdk.models.blocks.block_elements import FeedbackButtonsElement, IconButtonElement, ImageElement
 
 from . import STRING_3001_CHARS
 
@@ -1560,10 +1560,14 @@ class CardBlockTests(unittest.TestCase):
     def test_document(self):
         input = {
             "type": "card",
-            "icon": "https://picsum.photos/36/36",
+            "icon": {"type": "image", "image_url": "https://picsum.photos/36/36", "alt_text": "Icon"},
             "title": {"type": "mrkdwn", "text": "Lumon Industries", "verbatim": False},
             "subtitle": {"type": "mrkdwn", "text": "Committed to work-life balance", "verbatim": False},
-            "hero_image": "https://picsum.photos/400/300",
+            "hero_image": {
+                "type": "image",
+                "image_url": "https://picsum.photos/400/300",
+                "alt_text": "Sample hero image",
+            },
             "body": {"type": "mrkdwn", "text": "Please enjoy each card equally.", "verbatim": False},
             "actions": [
                 {
@@ -1575,6 +1579,24 @@ def test_document(self):
         }
         self.assertDictEqual(input, CardBlock(**input).to_dict())
 
+    def test_image_element_icon_and_hero_image(self):
+        block = CardBlock(
+            icon=ImageElement(image_url="https://picsum.photos/36/36", alt_text="Icon"),
+            hero_image=ImageElement(image_url="https://picsum.photos/400/300", alt_text="Sample hero image"),
+            title=MarkdownTextObject(text="Lumon Industries"),
+        )
+        expected = {
+            "type": "card",
+            "icon": {"type": "image", "image_url": "https://picsum.photos/36/36", "alt_text": "Icon"},
+            "hero_image": {
+                "type": "image",
+                "image_url": "https://picsum.photos/400/300",
+                "alt_text": "Sample hero image",
+            },
+            "title": {"type": "mrkdwn", "text": "Lumon Industries"},
+        }
+        self.assertDictEqual(expected, block.to_dict())
+
     def test_parse(self):
         input = {
             "type": "card",