If you need to print images that are as large as your wall but you owe a printer which can handle A4 sized papers only, than you should check out the website BlockPoster. This website lets you ’tile’ sections of your image across several A4 pages. It will let you upload an image and select how many pages wide you want your image to be. It then slices the image and creates a series of PDF file that you can print out to generate the various sections of your image. Finally, all you need to do is past them in correct order on your wall and there you have a huge poster!
The maximum file size that you can upload is 1MB, so you might want to split a large photo in parts while creating the final large poster.