Can bmp be used as a "world+image" in the same manner as jpeg and png? Do you want to try it?
I see on this page: http://udig.refractions.net/confluence/display/EN/World+Plus+Image
Looking at the geotools source code I see:
tempSet = new HashSet<String>(2);
BMP_WFILE_EXT = Collections.unmodifiableSet(tempSet);
So I would expect bmp to be supported as it stands?