Legal Question in Intellectual Property in California

In the abstract, it is illegal to copy a copyrighted work. That said, taking some copyrighted image from the internet and posting it on your wall, or pasting it into your scrapbook, would be at worst a trivial violation of the copyright law and it might well be legal under the "fair use" doctrine. Certainly nobody is going to sue you or bother you for what you do in the privacy of your own home. Just do not post or disseminate the images over the internet.