I sometimes make flyers to advertise new electronic resources, or create blog posts for the library. My favorite software for heavy-duty editing or rendering is the oddly-named GIMP, a freeware knockoff of PhotoShop.
You can do a lot with GIMP, from touch-ups to complex editing and pattern rendering. And, it’s free. I’ve tried PhotoShop on another person’s computer and from my intermediate-level user perspective, the two seem roughly similar. GIMP has a lot of great plug-ins, so you can extend the capabilities of the original.
If you’re interested in downloading GIMP for Windows, try this link: http://gimp-win.sourceforge.net/stable.html
UPDATE: GIMP version 2.8 is difficult to use. I would advise trying to get GIMP 2.6. You can download it at CNET: http://download.cnet.com/GIMP/3000-2192_4-10073935.html