Something easy to deal with.... something easy to house.... something active.... something interactive....

The first two that come to mind are the white's tree frog... they actually seem to enjoy interaction with their keepers, and the fire belly toad... too cute, too much fun to watch and also appear to enjoy some interaction and become quite familar with their keeprs.

Although the housing is different, each is very easy to keep, hardy and undemanding (compared to others), and considered some of the best "beginner frogs/toads" out there.

Truthfully, if I had actually thought about it, I would have set the 35 hex up very differently. I would have glued a "shelf" or "shelves" to the back side of the tank higher up, creating more of a "floating island" effect, to drastically increase the water level and volume to allow me more options.

Its all part of that "never satisfied" issue. You only limitations are your imagionation and your pocketbook. But, I strongly suggest that you decide what you want to keep, then build a proper environment for that creature. Take it from the voice of experience, building the enclosure first, then thinking about what to put in it, rarely works well for the creature or the keeper.