Hi Plantaquaria.
Looks like you are off to a good start.
It is not neccessary to have a water feature, as long as you are able to maintain a humidity level 80-100%. Some people just sit a small bowl of water in the tank and call it cool. A water feature in a 10 gal tank is tricky, I'm not saying it cant be done. Keep in mind that if you do decide to have a water feature with the pump in the tank, you will need to maintain accessability to the pump for servicing.
As for the acrylic lid, I would be very careful using acrylic. Acrylic will warp and bow, causing the edges to curl, and you will have an escape route for the frogs. I would strongly recommend having a glass lid for the tank.
As for small flowering plants, most of them will not stay small enough for the 10 gal. There are a few begonia species that would work, however some like it a little too much in these conditions, and require extensive pruning. I have heard of some poeple using African violets, haven't tried them yet.
Good luck with you tank, do you have an idea as to what frogs you are going to put in your new tank?
Keep us posted on your progress.
Cindy Dicken
Vivarium Concepts
www.vivariumconcepts.com
www.rainforesthabitats.com
www.texasdartfrogs.org