Unfortunately, the sprites I used (in a9sprite and tools) were designed by Detlef Thielsch. He pointed this out to me in a friendly e-mail last week, and has kindly said that I can continue to use the sprites for private use.
So, my apologies to Detlef for using his sprites without permission. (While I'm at it, I also apologise to Chris, for not using his.)
Thanks to both of them for providing the chance to make ROLF look half way decent and not like a bad copy of Arthur, which is how it would have looked with my attempts at icon drawing.