Potential tankmates

Following a black phantom-related disaster which killed off all but 4 (cause unknown - probably introduced infection or territoriality), my tank looks a little empty. It's 24x12x12", moderately planted, with a pair of kribs, 2 small upside down cats (possibly S. contractus for one of them, which is under 2", the other is about 2.5" and they don't hang around together), 4 black phantoms and 3 small guppies. Ammonia, nitrite = 0.
Any suggestions for something else (if that's even a good idea at all)?

Thanks,
momar