another problem with setting the camera for low rez, is sometimes you see a once-in-a-lifetime photo, and only later realize that you had the camera on 'Instamatic' instead of 'Ansel Adams' and wind up crying in your beer about it.
(true story- Recently got a ride in the nose of a B17; realized after landing that my 8 MP camera was still set for 640x480, high compression.
<insert sound of intense anguish, frustration and embarrassment here>
NEVER AGAIN. Even a a full install of photoshop CS is cheap relative to a couple of such missed opportunities.)
my advice: take a full-rez photo, crop closely, then resize to an "even" power-of-four number of pixels for best compression as a .jpg. then "step on it" by saving with the compression cranked up . . . a 160x120 thumbnail that is more than 5 kb is WAY TOO BIG. If you have the option, make sure the image is loaded in 1 pass- the cool 'interlaced' format that sharpens up as it loads takes more bandwidth.
(for the johnny-come-latelies to computers:) 160x120, 320x240, or 640x480 are good numbers to shoot for.
-Dan