Agreed. While you could write something in Perl to solve this problem, there's no point in re-inventing the wheel. if you don't have it on your system it's available from
.
On the other hand, it sounds like you may not be creating a mirror of the entire repository of pictures, just making a local mirror of a picture set whose members change nightly. If the latter is the case, there's a few fun ways to approach this:
Good luck with it. :)