Gamebanana Mod Page
Using the Character Select mod might show UI that is supposed to be shown after the title screen and not in the title screen, but it shouldn't cause too much issues.
This mod ports the vanilla SM64 title screen into SM64 CoopDX. Includes the title screen on start up and game over screen on game over. It works similar to Render96 v4.0's title screen on SM64 CoopDX.
Mario's title screen head is recolorable, but it's actually a built-in function to the game, surprisingly, so I didn't do any code to that part.