If the one will be a Central American Cichlid community why not have the other one to represent some of the African species? There are a few choices.
Malawi
1. Mbuna - lots of 4-6" colourful stock insanely active and a bonus is the breeding that will take place (if that interests you), having a lot of smaller fish with a large rock work would be of great contrast to the other aquarium.
2. Haps/peacocks - similar to the mbuna setup but with less rock work and larger fish (more attractive imo).
Tanginikan
1. Frontosa colony - there are multiple species/variations available, these are large and quite simply stunning when housed correctly.
2. Community - so many species have the potential to housed in you're aquarium depending on availability I would recommend looking at fish in the 4 - 8" range and having quite a lot of variation species like Altolamprologus calvus, Julidochromis marlieri, Neolamprologus tretocephalus, Neolamprologus sexfasciatus, Cyathopharynx furcifer etc are all beautiful and somewhat underappreciated.
Other Africans
Here it depends on whether or not you want a biotope, there are many species that don't get the recognition they deserve. Many of the Hemichromis species aren't particularly easy to obtain but as adults they steal the show. Some also grow to 10-12" and are extremely aggressive. Paratilapia are another species that isn't kept properly, a lot of the time they are lumped in with the Americans which can and does work but to be truly appreciated I believe they should be housed separately.