Anything that is not overly active and not small enough to eat will work out fine, just make sure you decorate appropriately.
Calvus will work because they are a calm and slow moving fish as well. Keep in mind though that they will need rockwork that will take up swimming space for the Frontosa. Frontosa can be clumsy, and if spooked can hurt themselves if there is too much decoration in the tank. Also that Calvus grow very, very, very slowly, so getting them on the larger side is a good idea. The 'lemon cichlid', which I am going to reason out is probably Neo. Leleupi, stands a very good chance of eventually becoming lunch to Frontosa(they have been known to consume fish up to half their length).
My personal opinion is that if you haven't kept Frontosa before try a small colony as a species tank in which they can be catored to. They are fabulous fish on their own and don't need a mix mash of other species to create a stunning display.