Hello there nekogaijin,
Apologies for the long reply, but there are several reasons for not linking to high res images of copyrighted works:
Legal: In the U.S., one can be a direct copyright infringer, but one can also be a "contributory infringer" by assisting someone in copyright infringement through a link or referral. An example would the the Pirate Bay web site, which does not host pirated files, but does link to those files on other sites (technically on the bittorrent network). In the U.S., this contributory infringement still breaks the law. See here for more information.
Availability of public domain works: The web provides an almost endless availability of public domain works, whether here (almost 100,000 are public domain), or on various other web sites. The Google Art Project, Getty Open Content, and others often provide these images at extraordinary levels of detail. So there are at least tens of thousands of images easily available at "brush stroke level" zoom for the public domain.
Availability of copyrighted works: While we work quite hard to correctly handle copyrighted work, there are lots of web sites which have no such rules. While I won't give you links or recommendations here, I can tell you I run into them all the time while researching, and often wonder how they get away with it. But for someone who is willing to use them, they are out there. Also, many estates and artists offer authorised examples. Finally, if it's "imperative" for your career, you can invest in a book here and there or pay for an image service.
It's a lot of work: You'll note that in general, we haven't prioritised lists of links around our site. Collecting a bunch of links, making sure they are still working, and keeping them organised is a fairly work-intensive task. Other sites such as Artcyclopedia, Wikimedia Commons, and Artist-Finder.com are devoted to this, and we probably won't delve into it unless we can do it in a better and more straightforward way without creating a lot of manual upkeep.
I agree with you that current copyright laws are ridiculous (thank Disney for much of that), but given the state of things, I have to think first of all about protecting the site's continued existence. Luckily, I think that you have many other options.
I hope that's a satisfactory answer, and thanks for asking!