Tanks looking a little empty

I've got a 90g tall (48long, 12deep, 18 high) with 2 jewels (4+ inches each male and female), 1 jack dempsy (7-8 inch, female), 1 common pleco (12-14 inch) and 2 catfish (4 inch). Since the design of the tank right now has turned into a slew of scattered rocks, i was thinking of redoing the tank and adding some more fish. The jewels and jack dempsey are staying, and the pleco and catfish are on their way out.
I was thinking of adding an oscar, a smaller pleco that wouldnt exceed 8 inches, and some other cichlids. Or will the jewels and jack be sufficient? Any suggestions?
thanks to anyone who responds