I don't get to change the backgrounds on my home screens but I do have them customized with widgets. I've got five screens (L to R):
1) Entertainment - Games, Music widget, Kindle.
2) Calendar - Got a grid calendar going with colors and whatnot. 4x4 Widget.
3) Home (Default) - Widget to turn on/off wifi/gps/bt/brightness/autosync, date widget, weather widget, Juicedefender widget
4) Communication - Handcent widget, MSN, Youtube, Facebook, Twitter
5) System - Everything to do with settings/accessing things in the phone from a "tech" perspective
All - Along the bottom is maps, handcent, xscope (internet), and google mail.
I've sorta kept all those through all the different home products I've used. Organized and awesome.
Need better backgrounds though....