First, how do you find the missing ones? There are hundreds of thousands of imageshack pics posted on the site, you can't just browse a page to see which ones are missing.

Then, you have to find the pic in the "folder with all the pics". IMCDB consists in more than "few pics".
There are about 1500 pics posted on Imageshack PER WEEK.
So in my backup disk there are few hundred of thousands of these.

Then find which one is the missing one, replace the code, etc.
For one pic it is quick, but if you have hundreds to replace it takes few hours.