I have a friend who loved my OC probably more than I do judging from that one time she wrote me an essay on why I shouldn't kill off my OC. She's an artist as well, so I'd get drawings of my OC and alternate universe ideas from her. Over the years, she had slowly becoming my wall to bounce ideas on and even helped me to become a better artist and storyteller, which I am grateful for! As for the reward, it's probably same as yours which include doodles, work in progress and work that I would never share online.