Here is a link to Mystery Meat template.
Mystery Meat Motto
"♩ see the photo or render, click one link, get the file ♩"
Mystery Meat is Library jargon and part of Documentation Policy, meaning a link to a link to a zipped file buried in a sub-sub-sub directory, as opposed to 'see the photo or render, click one link, get the file
PDFs of images can be Mystery Meat. PDFs of stuff which can be entered into the wiki are good. PDFs of stuff which is necessary to be printed out at scale in order to be useful is good, like paper you glue to wood before drilling the holes in the wood.
Even then, you want a large image of the thing you're printing out.
Tarballs of parts are Mystery Meat unless there is a photo or render of the parts right next to the 'see the photo or render, click the link, get the file
Foreign Mystery Meat
Foreign Mystery Meat is a deep link to offsite content. This is bad, because it is impossible for other RepRap User Developers to take what you wrote or designed and make it better on the wiki without accidentally introducing forking, mirroring, and versioning issues.
Imagine if the country of England was hosted on another website from the rest of Wikipedia. http://en.wikipedia.org/wiki/England
Now imagine how frustrating it would be to cross link or improve the entry for England, when that's on another website.