Been playing around with various achievement art and colour combinations by for some reason I can't get one that I'm happy with, I know it was a way to get money out of people but I wouldn't mind MS selling themes like they did on the 360, just for the fact of a more varied choice...anyways....

what does everyone use and look decent? At moment I'm still just got a black background and light blue tiles

I have pink tiles and found a pretty cool background (I think on Reddit) that makes the menu look like the LCARS interface from Star Trek. Cool if you're a Trekkie.

Won't let me post an image for some reason... getting an error. Here's a link.

I'm using this South Park wallpaper - looks great imho.

South Park Wallpaper

I'm boring so I use a black solid background and the default green tile color. That is how I prefer it, keeping it simple.