Alternatively,
EQGExport.
If you just want to change images, you can save them as PNG to upload them and they'll work, although they'll still need to be named "whatever.bmp" or "whatever.dds" unless you change the data in the WLD file. May need to be flipped upside down, though, assuming the original is really a BMP and not a DDS just called BMP (they were lazy when they updated textures etc)