After hacking the Amiga 100 Most remembered C64 tunes to bits I've recovered not just my C64 Monty on The run pic, which I'd lost for over 10 years, but also one I'd forgotten about - my Max Headroom pic!
After decompressing the demo, I poked around for a bit. I couldn't find any Amiga bitmaps, then realised that the pictures must be in the original koala painter format.
By luck I managed to extract the very first picture in the demo, then through a bit of detective work and much trial and error I managed to recover all 26, including three of mine!
The background colour value was missing from the pics, but that was easily figured out.
Hurrah! Now I can go to bed.
Thanks for all the help, sorry I couldn't get the demo actually working, but at least I've got my artwork back after all these years.