Shell dwellers are small cichlids from Lake Tanganyika in Africa. There are several species and they live in old empty snail shells. Males have a territory that is home to a number of females.
I don't have any pics but if you do a search for the following you should see some pics.
Apistogramma agassizi, A. borelli, A. cacatuoides, A. trifasciata
Nanochromis nudiceps, N. transvestitus
Pelvicachromis pulcher, P. subocellatus (the Moanda form is nice), P. taeniatus, P. humilis or humulis (not sure on the spelling of that one)
Aequidens dorsiger, A. curviceps
Crenicara filamentosa
Julidochromis dickfeldi, J. transcriptus
Lamprologus or Neolamprologus brevis & multifasciatus are the shell dwellers. Check out the rift lake cichlid section for others.
Have you thought about keeping other types of labyrinth like betta imbellis or coccinea. They aren't as agro as the B. splendens and can be kept in groups in a planted tank where they often breed. Licorice gouramis are nice fish too if you can find them, as are chocolate gouramis.
I did a spell check on this and just about everything was highlighted. Stupid spell check doesn't like scientific names