From Block Posters you can create any size wall posters from any size images you have. You just need to Upload an image from your computer and choose how many sheets wide
you would like your poster to be once printed. Once you’re happy with your selection, you can download the PDF file containing your newly created images and print each one massively blown up, resulting in a huge pixel poster to stick on your wall …

You can see more posters created by Block Poster in the poster gallery and click here to upload your image to create new poster. Then Slice your image and the last step is download images.

Click here for Block Poster’s website