The blog icon is the single image that will appear at the beginning of the associated blog post, Blog List, and Blog Page content areas. To upload the image, click Edit next to Excerpt inside any blog post at Content > Community > Blog.
Go to General > Configuration
Search for 'blog icon'
Click to open Blog Icon Maximum Width
Update the Blog Icon Maximum Width field
Click Save
Tip: This blog width does not apply to images prior to the change. To have the blog icons conform to the new width, delete the old logo in Content > Community > Blog. Then, add the new icon.