thats cool, ive been wanting to do a pico tank. as far as inverts id pick dwarf blue legged hermit crabs. those guys are soo cool and look nice. they stay small too which is nice for a pico tank. crabs id stay away from since they are opportunistic eaters and personally ive had bad luck with them eating corals. sexy shrimp would be cool but i feel like what ever fish youd get would eat it since they are soo small.