iWatermark
If your looking for a way to convert a bunch of images to use numeric format, such as 1.jpg, 2.jpg, 3.jpg etc.. You should look at iWaterMark by Script Software.
iWatermark has lots of cool functionality, but I just discovered the renaming functionality. This is great for testing images in applications where you don't want to type in long names. Also useful for renaming lots of files downloaded from the internet.