Hi Garen Cervantes - Which avatar are you looking to modify? I'm looking at a standard blog layout:
The blue circle icon at the top (next to "More blog posts in") is the standard group icon. If you're not in the cloud and your blog is inside of a space, you could customize this.
The blog icon (next to "Customer Success Program") would be the same - not in cloud, only for spaces.
The user icon (next to the TI Automotive title) is tied to the individual. What the user has for an icon will appear here.