Are there any alternative icons for FastStone Image Viewer?
No, there are no alternative icons for FastStone Image Viewer. The only thing you can customize is the SKIN alternatives. The software offers you the possibility of switching between various developer-created skins. It might not be much, but the colors of the interface will change a little. You can change the interface through Settings > Skin. The are a couple of styles already available.
Download application: http://www.faststone.org/FSViewerDetail.htm
Yes you can, with a .exe/.dll resource editor! :P