Here you will find some skins for both Spider-Man and Green Goblin as you have a playable Green Goblin too in this game. Recent updates on Peter 2 suit
How to replace textures?
After downloading the following file, go to Documents/Dolphin Emulator/Load/Textures/GSME52 and paste only the icons, not the folders. Have fun!
Link to Spider-Man 2 Skin Pack: Moddb.com
Link to Spider-Man 3 Skin Pack: Moddb.com