Thread:GandalftheTurquoise/@comment-29360236-20161026222338/@comment-25330335-20161030144517

Open the .jar of the mod with a program like 7zip or some other archive reader. Then you'll get the mod files. The file for the in-game skin of the cup is in assets>lotr>items>skullCup.png or something like that. The actual item icon is in assets>lotr>textures>items>skullCup.png or a similar filename.