I know polystyrene (Styrofoam) and xps foam are generally used and are safe and can be purchased in bulk for cheap.
For the coating on the Styrofoam I used colored sanded grout, and you can also use quickrete concrete coloring to change the color of the grout and just buy it as plain white if you wanna color it yourself 
Got a lot done today so far! Had to make a trip back out to buy more silicone though because I always really underestimate how much I’ll need 
Going to do the rest of the background tonight and then let the whole thing air out for a while, then it’ll finally be ready to set up for Mirage 
Same, oh my god same. XD
This is coming together so well! That textured BG is gonna be so cool.
looks great! Love the naturalistic shale cliffs effect, like what the bearded dragons natural habitat would be, although if it were myself i would have gone with xps foam, because its a little sturdier, and leaves less of a mess, but with the hot chocolate grout the foam should hold nicely
also can’t wait to see it painted!
I really wanted to do it with xps foam but my local hardware store only had 4x8 foot panels and I wouldn’t have been able to fit those huge things inside my little car 
I most likely could’ve just had them cut custom size in hindsight but it will definitely be a consideration next time lol
Edit:
Its actually already finished! I have a seperate post showing the final result with our Beardie inside
totally, and for a quick recommendation if you go with xps foam in the future i would suggest giving the foam a quick pass with a heat gun, just to give it more stability
awesome! will definitely go check it out!
