Every month PosterMyWall runs a contest in which you can win a free 8x12" print (including shipping) of any one of your custom posters. All you have to do is create a poster and click on the 'Win a Free Print' button. That will register your poster in the contest. To win the contest, you need to have the highest number of Thumbs Up's on your poster. The best way to get those is to share your poster on Facebook and via email with friends and family (just hit the 'Share' button on the poster), and ask them to click the Thumbs Up button on your poster.
A contest usually runs for about 2 weeks. If by the end of that period your custom poster has the highest number of Thumbs Up's, you will be emailed a promotion code which you can use to checkout a 8x12" print of any custom poster that you like! You can even checkout an InstaCollage that you or a friend created (and shared with you)!