Postby Fish and Chips » Thu Oct 29, 2009 1:36 pm
Technically, unless I have been misinformed, all images of any kind should be subject to copyright. Yes, including the screencaps you took yourself or the magazine ad you found scanned to make your nifty little avatar or signature or the concept art to head your article on Why Cowboy Bebop is the Greatest Anime. However, most companies that I'm aware of don't pursue legal action against reproduction of single images, for whatever reason. I also believe American copyright policy has a clause for "Fair use," which allows non-rights holders to use images for reference, commentary, promotion, critique, and parody purposes.
Please note though, I am not an expert on American copyright legality, so don't take this at face value, do a little research yourself.
It would also probably depend on the image you're considering. Can I get some details?