I would heat the cage with a radiant heat panel and not even worry about trying to rig flexwatt inside the enclosure.

CFL or Linear tube fluorescent lights will help keep the air temperature up (by a degree or 2) if you don't want the viewing lights to mess with the cage temperatures look into LED lights.

I like the tile floored cages... I'm working on setting one up for my bearded dragon. I hadn't thought of putting any tiles up the walls, I might have to steal that idea

*This is not my photo, downloaded from a Google images search*

I think that this cage looks really good... but I would clutter it up a little more personally