Do you work primarily with pen and paper, or do you also work on the computer to do illustrations?
I ask because if you have manycams installed you could easily have your photoshop or whatever software you use in a window on your screen. Then you could draw something easily while on cam.
I was just watching another model do a sketch the other day. She started from a blank screen and went all the way through to finished product. All the while chatting...and complaining if she didn't like how something turned out and she had to erase it.
But during that time, in addition to normal tips, she did a limited run raffle. When she got 20 entries she'd pull one name to get a printed out and signed copy of the drawing in the mail.
I have very little drawing skills, so I thought it was rather entertaining watching her. I'd say go for it.