Post background per user

[Keviee.]

Hello Devs, 

I need a plugin that allows some groups of my choice to upload an Image from "Account Settings" to show in their posts. This image image should be restricted to a specific size. I mean the size of all images must be shown the same (max width & height). The image should show at the top of the post as a background. 

I have seen this for v3.0 but I want something simpler. Just an image for specific groups. 

Thank you