I'll throw my oar into the water with the faction that is suggesting something a bit smaller than a Convict. A Rainbow (personal favourite), Nanolutea, Jewel, etc. Jewels are stunning and underrated fish.
Dithers? Go with something inexpensive...

To get the most mileage from them, introduce them to the tank several days before you get your cichlid. Then, as you replenish their numbers in future

, try to re-arrange tank decor with each new infusion of dither fish. It's a technique commonly used to throw established cichlids off-balance when new fish are added to their tanks; usually the new additions are more cichlids, but it's helpful no matter what you are adding.
I like the look of small and big fish together. In the past, when adding small fish to the tank of an existing cichlid or other bully-boy, I've gone to the extent of removing the big guy for a few days when the new fish are added. This gives the newbies a chance to settle in and relax a bit, rather than swimming around frantically in an unfamiliar tank signalling I'M NEW...EAT ME with every motion. If you have a quarantine tank...and you should!...this is another possible use for it.