I think it helps paint a broader picture about the user. Bios are usually exclusively text, and you have to scroll people's timelines to see what they are about which can be time consuming and or not telling of who they are.

Having a gallery would help people highlight some things about them, maybe their work, memorable moments, I don't know... anything. 

In a way yeah it would feel a bit Instagram-y but this gallery would be a more "permanent" feature of the profile. You can edit it any time, but you don't need to scroll forever to get a visual idea about that individual and what they value.