
to the forum!
Now, with two angelfish in there, that limits your choice of small fish you could put in it. I'd say a small school (5-6) Bleeding Heart Tetras, maybe 6 Glass Catfish, you could put a small spiny eel, but I'm not sure. You might have to post in the Oddball Institute if you want a spiny eel. Pretty much fish that are bigger than the angels mouth (no neons or cardinals!)
For substrate, it depends on what you are comfortable with. In my opinion, sand is much better than gravel (and if you get a spiny eel, sand is a must), but if you don't want sand, just go with gravel (then no eels). It's entirely up to you.
According to some information I've read, Angelfish like a densely planted tank with lots of tall, reedy plants (such as vallis). Also, some carpets of Riccia would look cool. You might want to check out the planted forum section if you're still curious.
Rocks and bogwood would like nice in a tank like that!
Cheers,
GobyMaster