I've found the origins of some of Bruno's stock footage. Here they are:
First, in Emmanuelle and the Porno Nights, one of the vignettes is some sort of sexy carnival ride that's basically a fun house with the usual monsters and, because it's Bruno, naked people. The scary footage seems to be stock, and can be seen (sans nudity and rider reaction shots) on Something Weird's Monsters Crash the Pajama Party DVD. I don't know if it comes from any other source or is just library footage, but it sure surprised me when I saw it turn up in a Bruno Mattei flick!
Then I learned about the jungle native footage from Libidomania and Hell of the Living Dead. It wasn't shot by Bruno, he actually bought it from a mondo movie called Nuova Guinea, L'isola dei Cannibali/Guinea Ama. That information I got from the great mondo history book Sweet and Savage: The World Through the Shockumentary Film Lens by Mark Goodall. Definitely check the book out; it's a great read, talks about some movies I hadn't heard of, and even has an essay by Gualtiero Jacopetti himself!
Anyone else find footage from another source turn up in a Bruno movie?