The Wireless Bitmap format supports only two colors, and making images look good can be tricky. However, your favorite image editor might have a function for decreasing the number of colors, and it might even have a method of doing this called Floyd-Steinberg. One such program is Paint Shop Pro. Paint Shop Pro is inexpensive compared to others, and there’s even a WBMP plugin available which allows you to save WBMPs directly. You can download a 30-day evaluation copy of Paint Shop Pro at the link above. An other program is Macromedia Fireworks 4, You can download a 30-day evaluation copy.

256 color image
2 color image Floyd-Steinberg
2 color image No Dither