I don't think that a 14 gallon is too small, depending on its dimensions. I know what other people say about this, but right now I have 6 Zebra Danios in a 10-gal with 2 Corydoras and the Zebras are doing just fine. They appear to be happy, healthy and just as ornery as ever. Man, I love those fish!
If I had my druthers would I put them in a larger tank? Sure I would. It would give them more space to swim in, and brother do they like to swim! I don't feel like I'm being cruel to them in any way to have them where I do though.
As to what could go with them. Corydoras!!!!!!!!!!!!!!! One of my other favorite fish. The danios occupy the upper portion of the tank, while the corys rule the bottom. I'd say with that size tank you could easily get away with keeping 6 danios and 4 corys, no problem.
You might be able to add some small tetras or barbs, but not too many. You don't want to crowd your danios! Do you?! I could you give a better answer to this if I knew the exact dimensions of your tank though. That will help me determine its carrying capacity.