I think for a wall to auto load with a skin it has to be a .bmp.Most skinners dont include a .bmp,they are too large.They might include a .jpg,but the last time I checked,they wont auto load unless you convert them to .bmp.And they would have had to make sure to point Windowblinds to the correct image.Some just include the image with the dl.Most dont include the wall at all.
