SDL_image is an image file loading library. It loads images as SDL surfaces, and supports the following formats: BMP, PNM, XPM, LBM, PCX, GIF, JPEG, PNG, TGA.
Images provide the basic visual building blocks for any user interface. Colors and fun shapes are the stuff that we as kids looked at for hours at a time while trying to shoot down big aliens and rescue pixelated princesses. Now it's our turn to make the images that others will remember later in life perhaps. Now how do we get this dang images into our SDL programs, and be flexible in the handling of the images so that we don't even have to worry about what various formats they may be in?
This is where SDLimage makes your life easier. This document doesn't help you make artwork, but it will give you the functional knowledge on how to get that art into your game. Now go forth and make your Stick Figure of Justice, someone else might fill in for your lack of artistry, at least you won't have to make much of an effort to include the new and better art into your code.