Welcome to DPC. You now have completed your first Challenge. Congratulations. The first one is always the most difficult. And I sure do like the colors you chose.
You created an interesting picture here, but perhaps an unsettling one for our viewers. Your selection of this partial mask view may have left some folks wondering what else they should be looking for. But, of course, if you had photographed the entire mask, you might have run afoul of the "Other People's Art" rule. One of your commentors suggested a more symetrical view. Now that might work, too.
Your image comes across as soft. Even with IS, sometimes it's a good idea to brace your camera or use a tripod on these long exposures and 1/15th of a second really is a long exposure. If you don't want to use a tripod you might think of boosting your ISO from 50 to 100 or even 200.
All in all, I'd say this is a creditable first entry and I expect you will have a lot of fun with DPC in future challenges. I'll look forward to seeing more of your work.
Just my opinion: In using the portrait orientation, I would have cropped this so the mask was perfectly vertical and split right down the middle.
As far as backlighting is concerned: Yes it is lit from behind. In a classic backlighting picture, there are shadows in the foreground to contrast with the light. This doesn't depict that.