I don't know if you mean the player character's head icon on the lives HUD ot the player character's head icon on the minimap, but I do know they aren't textures, so you can't open/view them in the texture editor. I'm having a similar problem with the camera buttons and the Power Meter, which are the same kind of files. IIRC, NSMBe could open that kind of files (I could be wrong here), but if you can do anything to edit them in SM64DSe, I don't know.