Discus need to be in bigger groups than 1 or 2. I also would not put them in that tank unless you want to devote the tank to a small collection of adults, but again, that's my opinion only.
Like I said, look into pearl, moonlight, and snakeskin gouramis. Snakeskins get to an admirable size, though pearls are my personal favorites out of those three.
As far as "sharks" go, a single red-tail black shark (Labeo bicolor
, I think) should fit the bill. Very attractive fish, though they do not get along with their own kind or with other "sharks."
Alternately, try to find or order some Puntius denisonii
, red-lined torpedo barbs. Some of the most beautiful barbs and indeed freshwater fish I have ever seen. To see a school of them (6" I think is the maximum size) in a well-maintained tank would be quite a sight! However, I have not kept them myself so I cannot give you an opinion on their safety alongside any long-finned fish.
Also, guppies and platies would be fine somewhere in that original mix, IMO