1. Make sure the icon is .blp or 24bits .tga Use WC3 Viewer (a free tool you can download in the art section) to convert the icon format if it isn't a .blp already)
2. Make sure the paths are Correct! The correct path for all icons except for main icon name at the end is: ReplaceableTextures\CommandButtons\BTN*iconname*
3. If its a .tga/you want it a .tga , make sure its 24bits. Irfanview converts the icon format (except .blp) to a working 24bits .tga