There's quite a large sub-culture within the RV community that focuses on bus conversions. Searches at rv.net or irv2.com forums will yield some info. There's lots of specialized sites like busnut.com. Mostly focused on true full size bus conversions, but the systems are the same for converting a small one.

One of my recent favoite conversions is a bus called "Odyssey", a converted Neoplan Spaceliner. There used to be one like it every year at the Runoffs. I like the two story front end, and large basement. Add some slides, and a winning lottery ticket, and I'd be all set. Odyssey