A single pair of Jewels (Hemichromis guttatus) would do better in a 30gl minimum. Not only are they nasty when they breed, they are prone to marital spats and get big. 5 or 6" might now seem like much but they'll definitely look cramped. H. lifalilli might do ok in a 20gl long since they max out at about 4" but bigger tanks allow more room for error should they not like one another.
Kribs, Pelvicachromis pulcher, would actually be perfectly suited to a 20 high or long. IME they don't do well long-term in a 10gl tank but are wonderful with the little extra space even a standard 20gl allows.
For a 10gl you could stock with a trio of multi's, Lamprologus multifasciatus. They're not the prettiest little fish but their interesting shell-dwelling and colonial behavior has made them a hobby favorite. Only gripe I'd have about keeping them in a 10gl is that they will quickly populate the tank and dozens of tiny shell-darting fry aren't easy to move out.
Lamprologus brevis is another shell dweller you can keep in a 10gl. A pair, trio (1M:2F) or possible 2 pairs may reside peacefully in the tank. There are several geographical variants of this species, one of which may appeal to you more. I personally love the "sunspots" from Ikola. The newer brevis from Kavalla are very nice too almost combining the "sunspot" with the "zebra" look of several other variants.
A trio of Lamprologus similis might do it for you. They're, in most people's opinions, prettier than the multifasciatus but they do not exhibit a colonial family relationship were previous generations of fry help look after the newer.
Maybe a pair of Lamprologus caudopunctatus would be better? The redfins are very popular, they almost never take a bad picture. A very beautiful little fish. Not a true shelldweller but they will use shells given nothing else (such as small caves) to use as a spawning site. Only problem is that they
might get too aggressive for one another in a 10 and a 15-20gl may be a better option.
Now, to stray from Africans, perhaps you'd be interested in some blue, gold or German blue rams? Mikrogeophagus ramirezi is a very colorful South American dwarf cichlid who would be happy in a 10gl tank. A single ram or pair along with a small school of tetras such as neons would look wonderful in the tiny set-up.
Apistogramma trifasciata is another tiny SA dwarf perfect for small-tank living.
And, well, why only cichlids? Dario dario or the "Scarlet badis" is a beautiful little anabantid, cichlid-like in looks - very much like a very tiny Laetacara species. Maxes out at 1", enjoys a heavily planted tank without heavy filter flow and is surprisingly easy to breed. You can house one or two males and several females in a 10gl tank packed full of java moss and they wouldn't be happier. The only catch to this wonderful little species is that they are hard to find, though incredibly enough relatively cheap. I bought mine for $2 each and fell absolutely head over heels for them! Being that they are hard to find they are also in high demand among Badid enthusiasts.
20gl tanks would allow several more options.