For shelves, you can add some T fittings along your frame so you can attach a few horizontal pieces of PVC to support the shelves. I would also suggest adding some 1x4's that span from one top corner to the bottom opposite corner on each side of the cage to help prevent wobbling when you move the cage around.

This guy posted how he did his iguana cage with PVC online, so you might find some ideas here.

http://lizardcages.fws1.com/minicagedoor-plans.htm

Post pics when you're done!