Angels are a mistake....you're just beginning this hobby, go for fish that aren't as delicate or aggressive as angels.......
Do you think that the upside down fish you saw may have been an upside down catfish? They're very good community fish and would be ok in a tank the size of yours.
I started out thinking that I was going to make a "saltwater looking" tank....but in the end, I realized that it could never be that....so I got over it, and did the nicest freshwater tank I could....
For example....I think that plants are a great idea, they're attractive and very good for the health of the tank....but you should realize that saltwater tanks can't have green plants.....they won't grow in that environment- so just by having plants in there will sort of be a tip-off that it's not saltwater.
Another thing is that most freshwater fish simply don't look like saltwater fish.....
Cichlids (which include angelfish) can have some very impressive colors, but many of them get very big and they have a very distinct body shape...... They also tend to be aggressive.
I think that freshwater puffers are very cool looking....but they're super-aggressive, so they really need to be kept by themselves.....They're also really brackish fish...which means that you'd need to have aquarium salt in the mix......Only some species are 'super aggressive', freshwater puffers are just that, freshwater. Not brackish.
Do you want a community tank or a semi-aggressive or aggressive tank?
The more aggressive the tank, the more spectacular the colors can be, but the more trouble you're asking for......
Tiger barbs are very attractive fish and they are good for semi-aggressive communities....you need to keep them in groups of AT LEAST 5 to keep their aggression towards others minimal.
Livebearers such as swordtails (I like the lyretail), platies, and guppies, and endler's livebearers (which are fabulously florescent in person) are very colorful...but they reproduce like rabbits, so if you get them, you can very soon have an overpopulated tank..... Unless he cleans out the tank of fry every once in a while, plus most fry get eaten within a few days anyway lol
For bottom dwellers, I've recently seen freshwater gobies that look like they belong in a saltwater tank....very cool......and many kinds of loaches are quite striking and have an interesting body-shape. Correct me if i'm wrong, but theres no such thing as a true freshwater goby
You can also add colorful shrimp to a not-very-aggressive community. Cherry shrimp are very cute (look like tiny lobsters, but are totally fish-safe)...and bamboo shrimp are awsome....
If you're getting an aggressive community, you can even consider getting a blue crayfish.....they're bright blue- very cool....but don't trust them with little fish, because they'll ambush them in the night.Amen on the ninja crayfish, also they get conciderably huge
If you really really want to get a cichlid....I'd suggest looking into getting "ram" cichlids. I have a variety called German Blue Rams. They're colorful (yellow, black, red, and irridescent blue), pretty, have personality, and, possibly most importantly, will NOT outgrow your tank. Bolivian Rams and Keyhold Cichlids are also good choices....look them up.
Let us know what you decide to do.