Well, I'll take on the ones I know at least.
As far as openbox goes, you'll have to get something specifically suited for background changing. Esetroot, feh, and others are pretty good for this. I use the pinboard feature of ROX-Filer to accomplish this. That's how I pull off desktop icons as well. As far as desktop icons, iDesk will do the same thing.
Your other questions...good luck! :P