Yes, I noticed that the two backgrounds used for multiplayer mode (lobby and setup) are skinnable, but I tried to discover the filename for these two but incorrect. The reason why these backgrounds are skinnable is that your skin sprites were used during lobby and in setup. In Special Mode selection screen it's skinnable as your back button was used during the selection. When someone discovered the options screen was skinnable, I discovered that the background for the Special Mode selection background was skinnable as the sprites for the lights were drawn over the background but not the header. I then discovered their filenames, and further that mode images. I hope that the two backgrounds for multiplayer mode are skinnable, but needs their filenames to be guessed.