Get yourself a Savannah monitor. Those get pretty big, eat rats, and can become dog tame. They are really messy, and you couldn't really decorate it very nicely, he'd just tear it up.
Or you could get yourself a small colony of bearded dragons, I bet you could put 3 or 4 in there, although, I'm not expert on them. Ask in the Bearded dragon forum, I suppose there is one, if not, lizards in general. That's a pretty impressive sized tank, I think it would be a waste to use it for a ball python. With Beardies, you could decorate it real nice with a desert type scene, those things look pretty cool, if you have time to maintaince a lizard.
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1.1 Jungle Carpet Python (both gorgeous)
1.1 Ball Python (normals, he said proudly)
1.1 Corn Snake (Okeetee, Amel)
0.1 Gray band Kingsnake (Blairs)
0.1 Desert Kingsnake
0.1 Pueblan Milksnake (Apricot)
1.0 Bullsnake (my garbage disposal snake)
1.0 Rhodesian Ridgeback (Hondo)
0.1 Spouse (WC)
3.5 hatchling ball pythons minus 0.2
1.1 Checkered garter snakes, one albino, one het