How can I improve my bearded dragon's enclosure?

Hey guys, nice to meet you all Thank you so much Fishbone!!

I'll track down a camera and post a picture of her full enclosure later on today and get a shot of her sitting pretty. Also I finally tracked down a ruler to measure her with (simple things like this are easily forgotten around here, haha) and discovered she's more on the order of 11.2 inches from nose to tip of tail. Fairly dark coloration compared to other beardies I've seen, and she seems to be in good health for the moment except for this whole pooping issue.

I can switch her feeding schedule without much problem at all, but before I got any concrete answers on this I was way leery of feeding her too much and then discovering some sort of health problem because she wasn't pooping. The food page is fabulous! Funny story, I have the rest of that website bookmarked...it was one of the places I went to when I was first trying to figure out how to set up her enclosure.

And no, I do not have a UVB bulb; that was/is a lot of money I just don't have at the moment, but it's on my list of future improvements (so is a set of thermometers). Her calcium powder has D3 supplement included, at 100,000 IU/pound (calcium "not less than" 36%). I know the D3 supplement isn't nearly as good as true UVB light for Ca absorption but I figure it's better than nothing.

When I post a picture you guys will see what I'm talking about, but at the moment her tank is under a window; I don't like this setup at all, our windows are absolutely horrible by every standard. The house is usually a little cold unfortunately, and being under a window isn't helping the temp in her tank...if I have my way it'll be moved shortly. The rock is beneath the lamp at the moment and it gets fairly warm to the touch as the day goes on. Also, moving the branch doesn't work the greatest, it's only at an upward angle if I lean it into a corner and brace it with the rock. Kind of an awkward basking spot, but she does enjoy climbing all over it.