of course, with an art thread, depending on the res (though it kinda doesn't matter) the line between 'fair use' and 'technically bootlegging the images' gets tricky..
without going into names, I have had an artist (some time ago) not being too happy with high res scans of posters (A4 sized) being on a site of mine which was his work so I had to either use lower quality versions or not have them. Bit of a shame as they aren't stuff that is really getting used alot and it's scans from cheap-ish printing, but that's still stuff under 2 copyrights (the work of art and the subject matter of the art). so.. the within reason stuff has to be thought about of course. But I'm sure Eric knows a bit more on the tightrope walking ^_^