What graphics editor (preferably freeware ?) works for editing the .PNG graphics for category icons? I've tried MS Paint that comes with XP, but Rainlendar cannot load the resultant edited files. (I think it has to do with resolution change to 96x96 dpi, but I'm not sure.)

If options must be taken within the editor to make the saved file work with Rainlendar2, perhaps this could be noted as well.

Text from logfile:

12:51:27: [0:00:17.656] ERROR: Unable to open file: images/icons/icon-toothbrush.png
12:51:27: [0:00:17.656] ERROR: Unable to open file: images/icons/icon-small-toothbrush.png
12:51:27: [0:00:17.688] ERROR: Initalization of skin "Shadow4_new" failed.

Any editor which can write png files and supports alpha channels should work just fine.
Try e.g Paint.net or Gimp.

Thanks for the tip. I see both are highly rated on Cnet and I am eager to give them a try.