Did you save your skin in 24 bit mode from PSP? You should not change it to 8 bit / 256 color mode in PSP.
What size is your image before you start?
Normally when you save it as 24 bit mode it is about 3 MB.
Then run Bright over it and the filesize should be around 1 MB.
If it has another size then something is wrong with the image and IL-2 will not accept it and thus not show it.