OK, so I use a few really lame tools to grab files from google image search. I hope my thought process makes sense here.

What I really like to do is harvest images that are from digital cameras- with file names like DSCF0001.jpg, for example. I've read about people doing things like this from some talks at DefCon, and a recent article in Wired; I'm just taking my quest for lameness to a broader scale than my own photos.

It is very interesting to see some of the photos you find- weddings in china, some guy's hot rod in the Ozarks, and everything in between. some are really neat, a lot of them really suck. you could really get picky and go through all the photos, but honestly I like to paint with a shotgun blast, not a fine brush, so I don't care.

so, here's what I've got: a script that I nabbed from some forum online and tweaked a bit- my apologies to the original author, but I was unable to find the site where I grabbed it from to give you proper credit. sorry! if it's you, please tell me and I'll update this. it basically just fetches the full images from search queries; I like it. you'll need to install some perl modules to make it work; just type "cpan" at the terminal prompt and then "install module::name". it's really easy.
imgo.pl

a script to automate fetching of images in a progression; DSCF0001, DSCF0002, etc. it's pretty self explanatory, throw it in a work dir and go to town.
imgfetch.pl

a script that uses ImageMagick's "convert" tool to resize all the images to 50x50 shapes for use in a mosaic application (go figure.) It recursively goes through all the image directories and brutally resizes images if it can, and then copies all the resized pictures to a different folder. it also relies upon a shell script that it calls to do the converting stuff, just because that's what I had to work with. someday I'll rewrite all this into a single functional perl script, but then again someday I'll win the lottery too.
moveme.pl
resize.sh
on further contemplation, I find that Mac OS X has a built in app called "sips" that does better and faster resizing things. sheesh. time to actually write all this into one nice cohesive perl script.

So, maybe this helps, maybe it's dumb. your mileage may vary. it's a quick way to build up gazillions of source images that are all different, if nothing else!