The problem with many image editors is that they're large and cumbersome or they can0t edit batches of programs in one swoop.
This is not the case with GIMP which is an excellent batch processor for images and files that allows you to perform a whole host of functions with batch image processing in mind. If you need to manage a large number of photos and rename them all or at least change their location, then you'll certainly find some use for this program. One of the advantages is it allows batch processing of thumbnail resizing which allows you to specify a particular width or height or define fixed image dimensions. You can then superimpose text onto these thumbnails or photos (useful to stop copyright infringements). If you need your photos in a variety of formats, then you can also batch convert pictures to GIF, JPG, PNG, BMP, MIFF, TIFF, PCX or TGA. Best of all, you're not restricted to one format at a time . you can select a whole bunch and then specify what format you want certain ones to change into. The icing on the cake is an FTP client which, while not exactly sophisticated (or particularly reliable in terms of maintaining connections), allows you to upload your photos to the net as quickly as possible directly from the application.
A very useful tool for anyone that has to process batches of photos at the same time or needs a very lightweight photo and thumbnail processor.