Pictures are a relatively easy concept to understand. A picture on your calculator is simply a state of the graph that has been saved as an image. Picture variables can be accessed under VARS:4.
To store the current graph as an image you simply go to DRAW:STO:1 press enter, then choose a number 0-9 and press enter again. The 0-9 just determines what picture variable you're using (i.e. Pic1).
StorePic 0 OR StorePic Pic0
To display a picture you go to DRAW:STO:2 press enter, then choose the picture 0-9 you want to display. WARNING: This will overlay the picture over the current graph, it will not clear the graph first.
RecallPic 0 OR RecallPic Pic0
Creating More Complex PicturesEdit
Sometimes one graph window is not enough to completely draw your picture. Fear not there is a way around this. The first step is to get as much of your picture on the graph as possible. Then save this as a picture. Clear the graph and finish the rest of your picture, overlay the previous picture and save the whole thing as its own picture variable. This can be done several times to create very intricate pictures.