(Edit: sorry, I took too long to post and reinstated what others have said!) I personally wouldn't recommend an angelfish for that size tank; it is tall enough for an adult angel but there would not be much horizontal space (if the dimensions I'm aware of are correct, about 14in x 14in x 20in).
What kind of fish are you interested in? That would help us narrow down ideas for you. Do you like small, itty-bitty fish? Or a few larger fish (nothing monster big though)? Or livebearers? Maybe a type of cichlid?
You could get away with doing shell-dweller cichlids in that size tank, but probably only 2-4 at most due to the footprint of it. They are vastly floor-space oriented. Shellies are a nice tank setup; they are a little shy at first but will come around in due time usually. They need sand and, of course, lots of shells to live in and stake out territories
Or if you like tiny fish, there's a lot of them! But they can be pricey. Celestial Pearl Danios are shy little bitty fish, but gorgeous. You could keep a nice school of 6-8 in there, plus maybe a couple sparkling gouramis. If you have a good amount of freshwater experience you could try scarlet badis, but they tend to be finicky and best left to those with lots of practice in the hobby. They tend to only take live food and none processed, are very shy, and fragile in most cases.
Otocinculus or Pygmy cories would be good bottom feeders for that size tank depending on the stock. Oto's are better for mature tanks though, since they don't always take to algae disks.
A single dwarf gourami or 1-2 honey gouramis would be fun. Honey gouramis are absolutely adorable! Make sure if you go with them, you have a male/female pair/ratio if going with more than one.
If you want something that's fairly unique to most keepers, a dwarf puffer would love that size of a tank! They're very petite and usually can't be housed with other fish though, they're aggressive. But they are personable and will even eat small snails right out of their shells as a treat.
Hope this helps!