Here are the items that you can unlock with Uplay points in the main menu in Assassin’s Creed 3.
Note that the first item may be different for the PC and Wii U versions when they are released.
Assassin’s Creed 3 Theme – 10 Uplay points
Multiplayer Profile Items and Pouch Upgrade – 20 Uplay points
Ezio’s Oufit – 30 Uplay points
Multiplayer Profile Items and Night Stalker Outfit – 40 Uplay points
Check out my other articles for more unlockables in Assassin’s Creed 3.