I'm planning to empty out Charlie's tank, deep clean and then try a few new elements. A friend gave me a coyote skull that was left outside for 2 or 3 years to let nature clean it. It's never been bleached. I thought it might look cool in the terrarium, but I don't want to introduce a harmful element.
As long as it's clean and any decaying material has been removed from it, I don't see the harm. After a few years, I'd imagine any harmful bacteria has moved along. Might want to sanitize it with some heat to be on the safe side though.
I wanted to share how the tank turned out. I spent a chunk of time getting all of the excavator substrate out of the tank, then scrubbing it down, polishing the clean glass with newspaper, and finally setting it up!! Here's how the coyote skull fits into the décor.
Honestly, I don't think Charlie cares one way or the other about the decorations. As long as he has his two hammocks, he's a happy dude.
Also, I have to brag on my coworker. He's a library cataloger but he is a talented woodworker. He built Charlie's new cabinet and it's fantastic! The whole set up moved over to my teddy bear picnic wall and I hope Charlie loves his new digs.