Sprites
Let's briefly discuss sprites. In gaming, sprites are usually used for animation sequences; a sprite is a single image in which individual frames of a character animation are stored. We are going use sprites in our animations.
If you already have knowledge of graphics design, it's good for you because it is an edge for you to define how you want your game to look like and how you want to define animation sequences in sprites. You can try out tools such as Sprite Maker for making your own sprites with ease; you can get a copy of Sprite Maker at http://www.spriteland.com/sprites/sprite-maker.zip.
The following is an sample animation sprite by Marc Russell, which is available for free at http://opengameart.org/content/gfxlib-fuzed you can find other open source sprites at http://opengameart.org/content/platformersidescroller-tiles:
The preceding sprite will play the animation of the character moving to the right. The character sequence is well organized using an invisible grid, as shown...