More are coming :P I doubt we'll be including many more expensive ones for the time being but maybe :) You clearly need a way to lose more of your money. New build coming out today at some point, hold onto your butts!
A bunny might be a good pet ;) if you wanted to contribute your mod sprite I'd be happy to credit you somewhere. If you want to make mods separately then by all means go for it, though without the backend infrastructure (only available on official servers) it'd kinda have to be a texture only mod.