Depends on how thick the wood is. If it is more than 1/2" thick I would go with flexwatt or a radiant heat panel instead. Remember that both of these need to be used with a thermostat.
Melamine is pretty good for racks but not sure about custom cages. The nice thing about melamine is that it is already sealed. You can find it at home depot or lowes.
Glass isn't really all that expensive, it is just a pain to cut. If you are up for it, go with plexiglass. It is more durable, easier to cut and drill into, and it pretty cheap.