I'm going to use an older (freeware) version
of BMP2EPA. It doesn't include some of the features that the new version
does, but it works.
NOTE: The version I'm using (1.5)
only works with Award 4.51 BIOSes, keep that in mind.

BMPtoEPA
Now, we load up our BMP. If your pic is not up to
spec, it'll let ya know. The file size for our 136x84 image should
be 1742 bytes. Click on BMPtoEPA button to move it over to the editing
window.
Pick a color and paint! You'll probably notice that
you can't paint each pixel separately. There's a grid you have to follow.
Only one foreground colour per grid square. You may have to move certain
parts of your pic to accommodate for the different colors you want
to use. As you can see, we had to do it as well: