On your main page, I see images from at least three different sites not your own. That means that the chances are at least 4 times as great of something missing as if you had all the files on one site. Also, I see that the gifs.net images are missing. Since I have no problems accessing them directly, I assume they have sensibly taken steps to prevent misuse of this kind.
Well,well,well.I guess those sites with "free clipart" are not free to use.I guess I'll just have to take a bunch of pictures of my own and stick on the site.How lovely.
When they say "free" clipart, they mean "free clipart". Not "free bandwidth." So it is OK to upload a copy to your site, but not to link directly to the image.