okay, well I see you are a fan of this design much like myself. Now, the problem is that these storage towers have a gap at the top of each bin that is big enough for any arboreal geckos to escape through. Therefore, baby cresties can't be kept in these. However, most common terrestrial geckos seem to do great in them! But again, there's a slight catch. As I have found out the hard way, some baby geckos (pictus and leos) have been able to scale these bins to the top where they can escape. To prevent this, I suggest forming a "lip" around the inside edge of each bin. Adult geckos can't escape, just the very young ones that are as light as feathers, that they can get to the top with enough determination.
As far as heating goes, a simple strip of 11" heat tape wired and secured to the back of the rack should work perfectly. Of course use this with a temp. controlling device (ie. thermostat).
The racks that I have in my closet do not require insulation, as the closet maintains an 80 F ambient temp as a result of the heat tape. However, my room gets a bit cool at night and during the winter months, so I cut and secured some "foil insulation" that I picked up at Home Depot for $12/ 10ft roll. This forces the heat through the bins as opposed to letting it escape out the back. This should only be necessary if your room is a bit on the cool side though. However, check your temps once you get it setup and then tinker with it from there.
Here's some pics of mine....
Rack in the closet (note small bins not used for geckos. They will be removed and replaced with larger bins)
The rack in my room, showing the insulation used to keep heat in bins.
The rack itself (which will be duplicated three more times for an ever-expanding gecko colony)
Hope this helps a bit,
-Adam