Lizard

I don't think this looks like a Gecko. The body shape doesn't seem to match. However, I am not quite sure what lizard it is. Here are a couple of websites that might help with identifying this guy (or gal):
http://www.californiaherps.com/texas.htm... (scroll down and click on names for images)

http://www.herpsoftexas.org/view/lizards...

http://en.wikipedia.org/wiki/List_of_rep...

Good luck and cool spot!

Are you sure that it is a geco?