RHEL, Ubuntu, & Debian cover the vast majority of enterprise installs I imagine, and provide a solid testing base for developers in the Linux business software space.
Maybe you add Gentoo, some post-CentOS clones/forks, or other more niche industry/workload specific distros, but how you do skip Debian?
This is 98% the right answer, but you drop them somewhere that keeps them intact, and believable enough so that people take them, and spend the rest of the weekend going to thrift stores trying to find an external floppy drive, and the next month trying to figure out how to get their iPhone to mount it.