Can't have clown fish- they are saltwater fish, not tropicals.
De-Niro, what dimensions are your tank? Ya need to make sure that any fish you get won't overstock your tank, over stocking results in bullying and unhappy, ill fish.
You'll also need to double check that any new fish you get will be compatible with the existing tank inhabitants.
If your tank is big enough, how about a nice schooling shoal? Cardinals are lovely little fish, extremely colourful, or perhaps harlequins?
If you're really interested in keeping a well maintained tank filled will happy little fishies I'm a member of a brilliant tropical fish forum and I'd be happy to pass on their address. Loads of brilliant advise on there including which fish can be added to others without them becoming snacks!