I kept these guys before there was the difficulties with the CITES status (which won't stay still now) and have a tendency to build many of my own cages...
First and foremost I found that bigger is always better. There are lots of herps which won't utilize additional room, or will utilize it so slowly as to make it somewhat pointless... The Solomon Island skinks I kept were fairly active most of the late afternoon and evening. They may not be the quickest species around but this wasn't the same behavior as an arboreal boid which might move a foot in twelve hours.
Basically the enclosures I put together were big plexiglass boxes. The interior dimensions were 4' x 4' x 4', with a cabinet underneath and a canopy up above. There was a fairly large hinged door on each side, with each door divided in half horizontally if less space was needed when it was opened.
I ran another strip of plexiglass perpendicular to the bottom of the enclosure near the back wall and drilled the bottom of the tank. Above the hole I attached a power filter pre-filter (plastic strainer) facing up, then dropped some hose into a small sump underneath and behind the cabinet. This was attached to a fluval which ran up and to a small spray bar which ran water down the back wall of the enclosure... The wall had been covered in very thin pieces of layered slate. The effect was very nice, but it had a tendency to become algae covered very very quickly (lots of oxygen + UV bulbs = Massive algae growth).
Since the sides were plexi, I drilled through and then used some screws and wingnuts to attach branches. These could be easily removed for cleaning and could be repositioned pretty much however I wanted. Similarly attached were assorted food dishes, by placing these at multiple levels around the enclosure, I got natural forrage feeding behaviors and the animals maintained a decent activity level and muscle tone. Switching the foods placed in any given dish also killed the tendency for animals to remember where the tasty stuff is, thereby skipping the foods which are good for them but not as colorful or flavorful.
The entire thing (except the front of course) was covered externally by wood panneling, which was easily removeable... This covered the doors and sides where the wing-nuts were holding the branches in place and gave the entire thing a more finished look. In order to get inside, either of the panels could be lifted off. This also meant that there was less of an area where the skinks were visually stimulated by the events happening outside the enclosure. The addition of this seemed to prevent the tendency to hide *constantly* even when awake and made the group I was keeping a lot more active.
The area in front of the sump was filled with bookshelves, every seam, seal and corner of the actual enclosure was covered so that it was not visible. I used fairly simple cabinet molding stained to match the remainder of the wood finish (oak in this case).
The canopy above the entire thing was finished to look similar to a mantlepiece and was supported along the edges of the enclosure with a double cross-support running through to carry the weight. The top of the enclosure itself was made of a galvanized, heavy gauge wire in 3/8" squares... The canopy housed flourescent and incandescent lighting, as well as a number of fairly powerful PC fans to assist with air circulation. Humidity wasn't much of an issue due to the waterfall effect down the back of the enclosure but I had placed a small fine misting head on some tubing in the center of the canopy which was connected to the fluval via a set of valves (I could turn the mister on by turning the waterfall off... or leave it on a slow drip... or have them both run at half strength simultaneously).
In retrospect I would have rather used glass on the front panel, as it's easier to clean but the whole thing worked well as it was... I filled the interior with branches coming in from the sides as well as up from the base, used a combination of orchid litter and bed-a-beast as the substrate and covered the small strip of plexi that formed the base of the waterfall with more broken slate chips. Toss in some cork bark and fake plants which could be rotated out for cleaning and it was a nice effect.
All of which was to house a small colony as a display... and is more elaborate than most people would want to get (although the whole thing only cost about $350 to put together, minus a few of the lights and the fluval which I already had avaliable). The basic elements are important though... Enough space to allow forrage feeding, humidity, heat and ventilation... Which kinda is what was originally asked about. The screen sides aren't required provided the animals have proper ventilation and enough to climb on. Heh.
