If you want a wall-size poster without spending a dime, print them yourself using free software and some basic tools.
Anyone who's ever shopped for a piece of art to hang behind the living room sofa knows that big art typically comes at a big price. Even if you pick up some mass-produced Ikea canvas, you still have to contend with fitting it in the car, or paying someone to deliver it to your doorstep.
If you have more time on your hands than money, there are some easy solutions for printing infinitely large posters from even the most modest printer.
The first step is the image. Whether you're going to print in black and white or full color, I recommend using a bright image with plenty of contrast. Maybe it's a picture of you at the beach or a photo of your dog at the park, but that dim photo of your friends at the club is going to look awful and it's going to use a lot of ink.
Also, recognize that printing out images that you don't own the copyright for, or have express permission to use may, be potentially illegal. CBS Interactive does not encourage or condone the illegal duplication or distribution of copyrighted content.
Once you have the image as a digital file on your computer, you're now ready to process it so that it's ready to print. The processing could be as simple as enlarging the image and segmenting it into separately printable sections. Sites such as Block Posters or Faster Poster specialize in this kind of basic scaling and chopping, and spit out a downloadable PDF that can be printed on any computer.
Personally, I find these kinds of photo enlargements disappointing. They get you close to the kind of result you'd get from a large format printer, but it's easy to spot the seams between the pages and the color printing quality when you're dealing with full sheets of color images tends to push the limitations of most consumer printers. If you're trying to print out a banner, or garage sale sign, it's fine. If you're going for something to hang on the wall that you will see every day, try this next technique.
Download a free program called Rasterbator. In spite of the name, there's really nothing salacious about this software. The official release is available only for Windows, but a ported version for Mac and Linux is also available, though it involves the additional installation of the Mono .NET development framework. This combo worked great on my Mac with a minimum of fuss, though the app is slow to launch.
Unlike the previously mentioned online tools, Rasterbator adds an extra step in the scaling process by applying a halftone filter to the image first, similar to images in newspapers or on billboards. The end result can seem abstract when viewed up close, but when seen at a distance, the effect is pretty cool. The abstraction also makes the poster easier to stitch together, since it imposes a grid across the image and provides seams with a degree of camouflage.
Whichever process you choose, the end product will be a stack of printed pages that you'll need to trim, and glue together. Expect that this will take some practice. The pro method is to use a nice, sharp paper cutter to precisely trim off the edges around the image and then glue the arranged pieces to a piece of poster board.
If you don't have the poster board or the patience, try trimming the edges from alternating pages, and then overlapping them onto the uncut pages. I used this method with a glue stick and then taped up the seams on the back of the finished poster to give it some extra strength.
So there you go. that's my best advice for printing up big posters using whatever printer you have handy. If you like the idea but need a little inspiration, check out the Rasterbator photo pool on Flickr.