Just a litle sugestion...
maybe give to admin/moderator a litle control to aprove (or not) this backgrounds, images etc before user publish in your profile.
I explain...in my site for example we have may users with ages in 9/15 years old. Kids...
Because this we have rules to care to any user put in the forum any images pornografic/violence etc.
And this amazing FULLY Customizable user profiles promisses...but maybe open do admin a litle possibilities to control bad actions from bad users...is a good ideia.
Anyway...forgive me my terrible english (i from Brazil) and consder this only a sugestion.
Best Regards 4all!