Advice: Silent Raffle Winner

[teashell.livejournal.com]

A few months ago, there was a raffle on a site like to roleplay on. The raffle was hosted by another player who wanted to bring together a bunch of artists/coders/etc, and their services would be the prize for various raffle winners.
I volunteered my services figuring it'd be a fun thing to do(at the time I had little-to-nothing in my art queue, and liked doing free requests). The raffle proceeded, people won, and one of the winners chose me to have their art drawn(as well as characters given by the raffle host).
I advertised 1 free headshot featuring 1 character as the prize(this was posted on the raffle). They asked to put their slot on hold, because at the time they didn't have a character they used a lot and wanted to wait until they did. I agreed to this.
Weeks passed and I had no word from them. After about a month they finally contacted me again, asked if I'd be okay with a certain species with an additional character being in the picture(a plushie). I agreed and asked for reference pictures... they never replied.

Two weeks ago, they finally replied and apologized, saying they had forgotten all about the raffle but wanted to redeem the slot. They wanted to change their previous idea and instead have a two-character headshot.
I've already replied to them and told them I would only do 1 character, and I had only agreed to their first idea because I thought it was only an accessory. It's been a week since then and I have no reply.

I would really like to cancel my services but I don't know how to go about doing so, or if it's okay to do. I feel like I should be able to, because it was a free raffle and no money exchanged hands, but I am also not the host of this raffle. The winner who contacted me received other prizes as well, so it's not like I can contact the host and have their winning status revoked and have a redraw.
How should I proceed? I don't want to have this draw out any longer than it has been, but I don't know if it's tasteless to tell them I've changed my mind and no longer wish to do art for them. Should I stick it out and hope they reply, or cancel and be done with it?