I may be able to get away with a 20g rule-wise, but I'm not sure I would have space for it in the dorm room. I've seen the room (It's the same one my brother's in currently) and a ten gallon is just about as big as I would want to go. I already planned on putting shrimp in the tank regardless of what else is in their, as I think they are cool, they will help to keep the tank clean and even if a few get eaten they are cheap to replace. Guppies were also on the list. I wouldn't mind a smaller catfish, and maybe a few kuhli loaches. Other than that, I would probably rotate one or two fish that would outgrow the tank after a few months. It would keep things interesting, and it would give me a wide variety of keeping experiences. Please note, I am really in no way motivated to make any sort of profit off keeping different fish. I'fd be more than happy to find a shop who would give me an even trade on a fish that I had grown out and a smaller one. This is purely for my own enjoyment while I'm stuck with just the one ten gallon.
and that is a wrap