The following images have been compiled by andrew_w of Tokugawa Corporate Forums
http://fullmotionvideo.free.fr/forum/index.php

Here are some OS-9/X68000 2.4 images:

These two are pre-installed hard disk images for XM6:

os9_x68000_2.4_pwin_hd.zip - PWIN, C compiler, and several extra programs installed
os9_x68000_2.4_text_hd.zip - text-mode system with AV-RIDER installed

These are the install floppy images in D88 format:

os9_x68000_2.4_d88.zip       - OS-9
os9_x68000_c_pro_3.2_d88.zip - C compiler

TOSEC has images of OS-9/X68000, but they're in an obscure format, which no emulator supports, and 
for which utilities are hard to find. I managed to convert them into usable images a while ago by 
using the restore utility in an emulator and then using some scripts to convert the raw images from 
the emulator into D88 images (they were a bit difficult to convert, because OS-9/X68000 formats its 
floppies strangely, and emulators don't seem to handle formatting floppies in non-standard formats 
very well). TOSEC also has images of OS-9/X68000 2.2 as well as 2.4, but I didn't manage to convert 
those (I can't exactly remember why they didn't work). I'll look at them again and see if I can get 
them to work.