Here are some new pictures of my 16 gallon. I added some plants, rocks and a piece of driftwood from my old 36 gallon tank (which is now empty).
Fred, my guppy cross, has some new friends and appears to be the leader of this new school. I bought 6 flame tetras, because I think they would stand out.
I decided against getting more puffers because I want a low maintenance tank (no special food, etc) and I was worried about Fred getting picked on.
One of the flame tetras came with a curved spine (didn't know till I got home), but my LFS said he had them since May and the fish isn't showing any signs of illness. He is a great swimmer, isn't thin and the school seems to accept him. I believe his curved spine is poor genetics rather than illness. I'm really hoping I'm right because the alternative would suck.