This test suite was grabbed from http://wvnvaxa.wvnet.edu/vmswww/bmp.html.

BMP PNG
1 bit (2 color)
4 bit
8 bit
16 bit
24 bit
32 bit
4 bit compressed
8 bit compressed
16 bit 555 bitfield
16 bit 565 bitfield
32 bit 888 bitfield
32 bit 888 bitfield version 4
32 bit version 5
32 bit transparent version 4

Note that as of December 2005, Mozilla and Internet Explorer do not support transparent BMP images.

The images (except for the last three and the OS/2 version 2 image) are from Jason Summer's BMP Suite.