Betta Fish: Stocking ideas?

I was wondering if anyone could help me stock my 20 gallon? I currently have a betta, (he is a male but he is nice and calm) two (male) African dwarf frogs, two mystery snails, one nitrite snail, and three otocinclus's. I'm planning on getting three more otocinclus's to help with algae. I'm preferably looking for something fun to watch and colorful. I'm fine with any fish. I have a 20 gallon long tank, sponge filter and live rock and plants, I'm added more plants soon, I always make my rocks into a big "cave" like structure. I have very friendly fish and got lucky with them. My temperature is around mid 70s F. My new 32 inch light is arriving tomorrow. The random lamp is temporary from previous lack of knowledge in the fish keeping community and I had to save for this light as they can be expensive