Since I have a copy of Amiga Forever 2016, I'm also planning to make a bunch of test files for Amiga formats that can only be UNpacked on other platforms.
So far, I've made a test LZX using the LZX_Y2KF.LHA release and I just need some suggestions for other things I can make with freeware'd Amiga m68k apps to build up a repo's worth.