Each bag has four graphics:
Code:
<Mapping ArtAssetID="bag" FileName="Invisible.tga" />
<Mapping ArtAssetID="bag_normal" FileName="Invisible.tga" />
<Mapping ArtAssetID="bag_pressed" FileName="Invisible.tga" />
<Mapping ArtAssetID="bag_rollover" FileName="Invisible.tga" />
Try changing the other tags to the same graphic (unless you want different images for rollover and pressed).