Here is a tip what happened today is a client asked me how could he print his poster for the shop. The advertisment he came up he wanted was much bigger then what his printer can print. I think it might be useful for many people.
I suggested you go to http://rasterbator.net/ and put in the details of the picture you want to use either by upload your own image or "cut and Copy" You then select your printer's paper size, and the number of sheets. You can have up to a 1000 pages but that might be pricey on ink and paper. I would suggest that eight is about as big as you want to go. You get quite a lot of options so it would be worth while experimenting first with the preview image before you print something.
They then give you the PDFs to download and print.