Great job! A few suggestions...
Placement of the temperature sensor should be in the middle of the keezer.
Paint the inside of the keezer with appliance epoxy paint to prevent future rusting.
At the bottom of the keezer, put down some plastic cushioned shelving liner to protect the paint.
One of the problems that I've addressed with my keezer is keeping the temperature even throughout, which also helps with ice build-up. You'd be surprised how much the temperature can fluctuate from the bottom to the top. In addition to having the keezer connected to the temperature controller, I've also connected a homemade fan that sits inside at the top of the keezer. The fan was made soldering a computer power fan to a cell phone charger. It'll only take one frozen keg on the bottom shelf until you decide to do this. It also keeps beer in the beer line from becoming too warm.