I think a 37 is a tall 20 long. In this case, I would either go with some dwarf new world cichlids or ditch the pleco (maybe both cats...don't know much about pictus) and go with a group of Tangs.
You may be able to keep some dwarf peacocks (maylandi, blue orchid) in the tank long-term, but the catfish will have to go (replace the chocolate pleco with an albino bristle nose pleco for algae control.. they only get to be about 4"-5" long max). You could probably get away with a quad of the peacocks and will thoroughly enjoy those fish. Any other Malawi fish (including other peacocks) will be too large/aggressive for a tank that size.
If you got rid of the catfish and went the Tang route, you could do a colony of shellies. You will love that tank, but they won't take advantage of the height. Unfortunately, most Tangs that occupy that upper strata need a tank longer than 30".
Alternatively, you could probably get away with a pair of julidochromis and a pair of Altolamps.... though this may be too tight for two pairs of rock-dwellers. Provide a few piles of small rocks with caves to establish territory.
Running full circle, a pair of apistos in a heavily planted tank with tetra dithers and cories is always a winner.
Thanks for the info on the choco, if it becomes too large I will give it to my buddy.