I've found that the problem isn't my custom graphics/wallpapers --- it must be something with Wineskin because ALL graphics look discoloured and pixelated. Take a look at the wrestler profile pics. They are all discoloured, yet they are the stock images that come with game. It's only when you click on wrestler profile pic that the pictures looks clear and in good quality.
This is in addition to the original problem - where any wallpaper graphics set I use also look distorted in the Options menu, and when the actual load screen appears, you can see saturated lines and fuzziness. In this case it's not that noticeable but YMMV whenever I load up the game.
EDIT: I tried switching the Wineskin Wrapper engine to an older version WS9 1.9.20 so that it matches what was available at the time, but this did nothing. Graphics are still discoloured.
Any thoughts/solutions?