let me see if i can get these all at once : )
the dirt, and general soil strategy, is laid out in a couple of FAQs at our site, please have a look. we use this dirt for monitors, Gilas, Uros, and snakes, it has lots of applications.
the wood stacks are also explained in the FAQ, although after gazing at the pics for a minute, i am going to go in today, drop the soil level on the basking side (with the wood stacks) another few inches so that i can add 2 or 3 more stacks.
the black plastic is a horse/cattle watering bowl, upside down, and there is an entry on the far side that you can't see. it serves as a basic hide area, and there are four more much smaller hide spots inside of that to provide true hiding spots, but it doesn't get used much at all, except for as a spot to start digging sometimes.
they do dig and burrow in the dirt, they are lizards 
we had access to a bunch of captive hatched Ornate Uros, so we set up 4 nice groups. we do intend to raise them up for a breeding adventure, and we do have interest in other species, but it is so difficult to get good captive baby stock in sufficient numbers, and we feel that is a key foundation step to working into a good productive group. for now, it will just be these Ornates.
i am excited about the breeding potential, but we are kinda just chugging away quietly right now, figuring out husbandry, animal needs, and possibilities...
-----
robyn@proexotics.com
Pro Exotics Reptiles