[TigerC10]

Imageshack actually doesn't name those files the same thing they're named when you upload them. Imageshack and other image hosting services rename the file to a bunch of numbers and letters. When you put in the request for an image by name, there is a custom CGI script that queries the database for images with the same name - then it outputs the matching image if it finds one.

The request for the image name is sent to a CGI script, and the CGI script spits out an image - this is how they can swap out the picture for a different one if the user has gone over their allotted bandwith (you know those pesky "bandwith exceeded" images). It's also why if you specify the wrong image name it will show a picture that says, "invalid image" or something. Do you really thing they go in and replace those pictures entirely every single time they have to?