So I'm not sure why I didn't figure this out ages and ages and ages ago, but I finally figured out why the 9th Anniversary Shadow Tileset bugged me when using it. If you take a look at the staircase/stairs, they're highlighted wrong. Place them next to a shadow wall, and you'll see what I mean. The UO standard is that the south side of an object is "lit" while the east side of an object is "in shadow" or darker than the south side. Yet, if you look at the shadow stair pieces, they are exactly the opposite: they are in shadow on the south, and lighter on the east. Not sure if the original assets for the 9th anniversary stuff still exist, but if the new artist could tweak these a little to bring them in line with the correct visual, it'd be awesome!