Skype games seem to be a big hit. I think games run by one of the RPPR guys would be cool, and as a higher level maybe a skype game with some of the crew? A live cast of a game could be interesting, so high-end backers get access to that and the mid-range get early access to the mp3 of it before it goes to the regular AP site. I think getting the guys, mainly Caleb, to do dramatic readings of obtuse RPG rules would be a riot. Just imagine a slight orchestral backing as Caleb and Tom try to read rules from Synnibar and Rifts.
Personally, I'd think it'd be really dope to get some RPPR merch, either as Patreon rewards or just as regular store stuff. The KC Green banners emblazoned on shirts and mugs would be great, along with posters, buttons, stickers, hell, even calenders could work. Stuff with original art from campaigns or Base Raiders would be cool, too. Though, I'm not sure what sort of legal issues might be involved with some stuff, like Know Evil/Tribes of Tokyo merch. Something to keep in mind at least.