I needed to bring the substrate high enough so that it would be more in line with the view-able area (as in the glass areas). That way if the geckos were on the floor of the enclosure, they would be visible if I were sitting nearby. I needed lighting and I needed to decorate it in a way that provided multiple horizontal and vertical perches. Multiple geckos means you need to provide multiple places of safety or they might compete or fail to thrive in general.
I considered painting a mural and decided not to because it would be a pain to seal it enough to resist the daily water misting my pets require. I considered a few other options: fabric, tapestry, yarn streamers (they look very cool if you use thick yarn in a natural bamboo-like color). Then I went to the bathroom and BEHOLD! My shower curtain. My tacky-but-who-cares shower curtain depicting a photograph of a jungle scene. Perfect. Waterproof, easy, jungle-tastic. Like a scene straight from New Caledonia. Of course I had to replace my shower curtain in case I decided to shower sometime.
When using great stuff as a substrate you can use it to anchor your structural elements (like limbs) if they are not too heavy.
What I used:three large cans of Great Stuff, a serrated steak knife that I use for crafts, a thick plastic drinking cup.
I also stuck three dried limbs into the foam to serve as trees. (Only two pictured). I jammed the third one in after the foam had dried.