Apartment Therapy recently reminded us about the Rasterbator. Not the sort of thing one might deduce from the name alone, the Rasterbator is a free easy-to-use service that allows you to upload any image to their site and they will send it back blown up as a series of pdfs. Now available in color, piecing the image back together results in a huge decorative poster and provides an alternative to wallpaper.
Rasterbate your image here.
Also on Cool Hunting: Rasterbator