www.halo-central.com Look for the downloads. They have a nasty assortment of brushes you can DL for backgrounds. And they have a Halo renders pack that will save you a retarded ammount of time making sigs (read-- you won't have to cut anything out...well...take time cutting anything out...)
Just DL the renders pack...then open anything with a background up in photoshop...use the magic select tool 3 or 4 times...and you're done.