[help] postbit background

Extremely easy. Please don't try to run a forum if you don't know anything about web design or development.

find ".post.classic .post_author" in global.css
change background property to url('path/to/image')
fix your background sizes or whatever

note: this makes all posts have the same background. if you want to change certain users to specific images, you will likely need a plugin (or for certain usergroups you can use template conditionals)