Good program for skinning?

I want to make custom skins for units but I can't find a good program for doing so. Can anybody tell me a simple, free skinning program?
I already searched multiple sites for the type of skins I need but can't find anything.

EDIT:
I found something I can use.

I don't really know of any skinning program.

I know that Image extractor can extract a blp and convert it into editable TGA which you edit with "the GIMP" (good gooogle search term) to make a new skin.

Hello Nashako.
Continualy scour forums for updates to all programs, and sollutions to bugs.