The cages shown for Cujo and Freddie are our cages.
Don't have any plans per se, but can certainly offer some input! These are things that we have discovered after 10 years of keeping iguanas and after having built four iguana enclosures, many of which we have had to renovate time and again through trial and error. 
Ramps and shelves are inexpensive and easy to set up, but they are unnatural to an iguana. Their nails tend to grow crooked because they are not meant to be lying on a flat surface 24 hours a day. It also causes problems with an iguana that has problems with toilet training. Most iguanas prefer to "bomb" their poop from a branch or similar surface, although many will learn to go down to the bottom of the enclosure and poop in a tub, but this is not necessarily reliable, because whenever you move the enclosure (either in a new room or a new house), the iguana changes its habits. So if the iguana decides he wants to "bomb" his poop, if he is on shelves and ramps, more often than not that poop is gonna end up on a shelf, a ramp or both and more often than not, by the time you discover it, the iguana has had time to walk through it and smear it everywhere. Basically, ramps and shelves are a nightmare to keep clean unless your iguana is perfectly toilet-trained.
Wood as a material doesn't work, no matter how well you try to seal it. So if you choose wood to construct the base of the cage, you will need to laminate the walls with a moisture-resistant material. There's a company called Habitat Systems that uses a hollow-core plastic to built their enclosures, you can check out their facilities here:
http://www.habitatsys.com/production_facility.htm
Also check out their main page, www.habitatsys.com. Their cages look pretty cool. Anyway, if you can find a similar material, it might be worth looking into.
You will also need to have some sort of screen in your lid so that your iguana can't get to the light fixtures, otherwise he can burn himself.
Do you have any experience in carpentry? Building an enclosure is no easy task, so I just thought I'd ask. if you don't, you really might want to consider just buying one, because there's a really good chance that you will end up spending more trying to build it yourself.
Been there, done that! LMAO
Julie 