If you’ve got access to a large-format printer, then that's great, but if not there are numerous cheap or free programs dedicated to printing long banners and posters.
If you can't or don't want to install new software, some print drivers will allow you to print "poster size" images directly, but if not there are other simple ways to print large target faces from small printers, such as with the aid of Adobe Reader, or MS paint (which is installed by default in Windows Windows 7.) A3 paper is great as it is almost exactly half the size of a 40cm target, but A4, 'Letter' and even 'Foolscap' sizes can be used - 4 sheets of any of these can be glued to the back of an old 40cm target for re-inforcement, or use 6 sheets of A3 for a 60cm face.
(Even the heaviest printer paper is much weaker than the stuff used for competition standard target faces.)
On Apple's OSX you can use Safari to print a target face to span multiple pages:
Open the target face in Safari.
Go to File -> Print... and then change the Scale (%) so that the image is the desired size. If you do not see the place to change the Scale, you may need to press the Show Details button. Safari will show you a preview of how the image will appear on each page, so you can see how big the resulting image will be. For the example, you can get the entire width on a single page, but the image will span 2 pages in length.
Choose borderless printing if your printer supports it.
Click print. Collect your target from the printer, trim away white space where needed, and then combine the different pages using tape or an appropriate glue.
In Windows, here’s what to do:
Save your chosen target face to a sensible place on your hard disk, or other storage, then open the saved file in Paint.
Select: Print -> Page Setup (Vista and 7), or File -> Page Setup (in XP)
Under Scaling, select Fit to: and change the setting to something like “1 by 2 page(s)”
Print the image from Paint, and make sure to select “All Pages”
The image at the left, in a rather too subtle manner, should show how the image will be printed - for normal printing it should show an image with a diagonal cross on it, representing the image, imposed on a rectangle that represents the paper. For a 1 x 2 page image, only the top half of the cross should be visible, i.e. it should show a 'V' shape.
Before you know it, you’ll have your new target printed. Now trim the bottom edge off the top sheet, glue both/all sheets onto an old target face and you will have a face that is strong enough for an entire session of shooting.
Valentine's Day Faces
Animal Target Faces
Guy Fawkes Night / Fourth of July / Independance Day