A little more info...
Excellent.
Here are some tips I looked up:
It is best to keep them square. It is suggest that you use 32x32 gif images. I'm using 128x128 without any trouble. If you have PSP you can take the images and resize them. Also if you have DXTbmp you can save it as an extended bmp 256 color and it will resize to the closest square size.
If you want to make it a real icon open it in MSpaint. Choose Save as and add .ico to the end of the name. It will then make it an ICON file
I would make them in 32x32, 64x64, 128x128, and maybe 256x256 but no bigger. Then see which looks best to you.