Is this your first tank? Only asking because some fish are more delicate than others.
I mentioned dwarf gouramis above, and along the same lines there are honey gouramis and pearl gouramis. It would be best to pick one of these, and just keep one male. I've heard mixed reports on their compatilibility with guppies though, maybe someone with more experience with keeping the two fish together can chip in on this.
I would go with a dwarf cichlid since you are missing bottom dwellers in your plan. There are bolovian rams, kirbs, and many different types of apistogramma (my favorite are cockatoo apistos). For a bit of a challenge, you could look into german blue rams, gold rams, and electric blue rams.