You need to save the file in 8-bit or 256 colors.
I bet you saved in 24 bit.
Easy to check: the BMP files should be 1 MB in size. I guess yours will be 3 MB.
You can transform your image to 256 colors in Gimp. But many skinners like to use Bright for this (in your case the program and not the plug-in).
This tutorial shows how to use Bright.
It starts with Paintshop Pro a bit, but how Bright works is for everyone the same:
http://www.simmerspaintshop.com/foru...ng-bright.html
I think you can run Bright on your current BMP to get the job done.
