That thing has been offline forever. Is there an alternative mirror or a backup of everything?
It looks like that was the site started by Mahuti and eventually moved to
http://arcadeartlibrary.com/arcade_art/ by Sirwoogie.
This site was originally started by Chris Newton (mahuti) of Barrett-Newton Interactive. He has now had to move on to bigger and better things. Now I, Sirwoogie, now have control over this site. It is still the place to share arcade art. I currently help Saint run the Build Your Own Arcade Controls (BYOAC) website, forum and wiki.
Unfortunately, the arcadeartlibrary.com site has been up and down numerous times in the last few years. (currently down)
Archive.org shows the homepage, but doesn't appear to have any working download links.
Scott