If I were you I would go for a larger species so you can see them and have it as a display viv. Your setup sounds great, can you upload any pictures?
Species you put in are completely up to you; any dendrobate tinc. Species would be a good choice as they are bold and active. Another option could be a phyllobates species as these are also bold.
It depends on how much you want to see the frogs really, smaller species such as ranitomeya are very beautiful but may be hard to spot in the viv.
The choice is yours! I wish you look with it all.