I'm an avid follower of virtuallyfun.com and right now the latest post is about installing AIX on QEMU. If you look into the qemu category ( https://virtuallyfun.com/wordpress/category/qemu/ ) you'll find OS X Server, Unixware and more.
The author, neozeed, is very friendly and you can leave him comments or shoot him an email and he usually answers pretty in depth.
As for OS 9, I'm not sure it is as refined and functional as SheepShaver on Windows yet, but I'm on OS X, where SheepShaver takes more effort to set up. There's a modified QEMU for enhanced OS 9 compatibility (I think more G3 emulation?) here, and people managed to install 9.2: https://www.emaculation.com/forum/viewtopic.php?f=34&t=9028
Link?
Or do you mean a copy of the ISO? For that I'd try archive.org or winworldpc
While years ago I would mainly use Virtual PC (I do miss its great GUI) and VMWare (and rarely bochs), qemu improved a lot and has (somewhat decent) support for so many more architectures. You can run Solaris for SPARC and Mac Os 9, for example.