I've noticed that two, common and cheap, card games are uniquely suited for use with icehouse pieces. Namely, Phase 10 and Uno. Both have numbered cards in each of the four Rainbow colours. Uno is a game most people have at least one deck of sitting around. And Phase 10 is pretty cheap and common these days, too. I'm sorry if I'm not the first person to point this out, but I thought I'd mention anyway.
Furthermore, I've found that by taking cards out of two decks of one of these games you can make a small binary (or three-person) Homeworlds deck -- for those days when even pyramids are too bulky to carry about. If you orient all the stars in a third direction not used by either opponent's ships, it works pretty well. I find I prefer the Phase10 cards to the Uno cards as their orientation seems clearer to me.