From the new
skinning pack for update 10 :
<Mapping ArtAssetID="buynow_button_highight" FileName="buynow_button_highight.tga"></Mapping>
<Mapping ArtAssetID="buynow_button_highight_ghost" FileName="buynow_button_highight_ghost.tga"></Mapping>
<Mapping ArtAssetID="buynow_button_highight_l" FileName="buynow_button_highight_l.tga"></Mapping>
<Mapping ArtAssetID="buynow_button_highight_l_medium" FileName="buynow_button_highight_l_medium.tga"></Mapping>
<Mapping ArtAssetID="buynow_button_highight_l_small" FileName="buynow_button_highight_l_small.tga"></Mapping>
<Mapping ArtAssetID="buynow_button_highight_medium" FileName="buynow_button_highight_medium.tga"></Mapping>
<Mapping ArtAssetID="buynow_button_highight_small" FileName="buynow_button_highight_small.tga"></Mapping>
Just link these new pictures to a blank file.