An useful skin needs 2 things:
-Looks good in game. It DOESN'T matter how it was done, 99% of the w3 players are not artists. Some skins may have well done textures, but in game they look like crap and nobody would use them. As I can see, Wormskull's are a few of those.
-The size. Most ppl like to use small skins instead of horrible 200kb size, especially if their game is multiplayer.
I look at skins from the view of a map maker, not a skinner, and I know which skins are to be used, which are not.