Hard to make any suggestions without some idea of his or your preferences. Does he like pain? Would you like to see him in pain? Are the two of you into humiliation? Bondage? Drag?

The list is only limited to what you can imagine and what he can do safely to and by himself. Like CBT, Chest or pubic waxing (hair removal) Body painting, Insertions (anal and penile), self flagellation. Panties at work (photos before and after). Search here in the forums and see if anything strikes your fancy.

Cheers
Twisted