Yeah I've had trouble getting entrants for an art raffle on here too. It's weird because I can see how many people view a journal, so I would get a pretty decent number of views but I ended up with only 6 entrants. I wish people here were more active and participated more. Anyway sorry your raffle didn't work out, but thanks again for making a drawing for me. Good luck with any future raffles, even if they aren't on here.

I was pretty sneakier with two 'art raffle' ideas.

• I had made a short list of people I'd want to do art for, and asked them specifically if they would like to a play a random chance game. Everyone got back to me. I've only started three out of sixteen images, but they're being done.
• Second time around I made a journal but was more constrained, is that people got 'two raffles' that I'd use random.org to pick out from the list. Only rule was they could only suggest kinks, given how the fandom views such matter I got the idea reading an article on social psychology but tl;dr not suggesting your favourite kink to be drawn is equivalent of letting your team down.

Take-away is to be Specific and Personal, and to also be inventive. After a while of seeing the same words over and over again people mentally turn off and stop processing what those words mean. It's the difference between "Open for Commissions" to "Hey Guys, do you want Art, this may be your lucky day!" /blunt example. I hope this helps or is in some informative.