1. A computer-implemented method of creating a shape collage, the method comprising: receiving a shape specification signal which specifies at least one desired shape, each desired shape having at least one shape boundary and a shape area; receiving image data which represents a plurality of images; and processing the signal and the data to obtain a shape collage of the images which at least partially covers and conforms to the area of the at least one desired shape so that the collage resembles the at least one desired shape, wherein the step of processing includes the steps of: creating a tree structure of the images wherein images are represented by tree nodes, the tree nodes corresponding to sub-areas in or near the shape area; processing the tree structure to determine locations for the images based on their position in the tree structure; evaluating by utilizing at least one coverage predicate whether each image is to be treated as being either within or outside the shape area based on its determined location, removing or hiding at least one image that is evaluated as being outside the shape area and leaving a placeholder node at the location of the at least one removed or hidden image to preserve the tree structure; and inserting the at least one removed or hidden image back into a portion of the area evaluated as being within the area by finding a tree node in the tree structure that is within the shape area and inserting the at least one removed or hidden image into an adjacent position in the tree structure.