Unless you’re opposed to having your tank(s) appear unnatural, nearly anything that is chemically and biologically inert is fair game for use as shelter for your cichlids. This includes items such as ceramic pots, various aquarium ornaments (e.g., ships, pagodas), artificial plants, ABS/PVC pipes and fittings, etc.
Most cichlids will take advantage of items already in the aquarium as places to hide or seek shelter such as submersible heaters, sponge filters, and filter return tubes, but you should supplement those items with additional material. Try what you like. In fact, if you’ll make notes of your cichlids’ behavior, you’ll quickly learn what they’re preferences are as well (e.g., do they prefer the white PVC or black ABS plastic, do they prefer a particular size of ceramic pot).
Also remember some cichlids are quite particular about where they’ll lay eggs. Cichlids may be egg scatterers, cave spawners, shell spawners, or even plant or gravel spawners. If you want to be successful breeding, find out what kind of spawners you have and make an effort to accommodate them. Giving them multiple options (types of caves, plants, or shells) increases the odds that they will find something acceptable and spawn for you.