Obtaining Media
Before sources can be explained in depth, there is one rule that should always be kept in mind:
Just because it is online does not mean it is free.
Media cannot simply be used without attribution if it is not your media. Owning your own media will be explained further in the page. That being said, this statement excludes everything in the public domain. The public domain is the realm in which works have either never been copyrighted, or they are old enough to the point where the copyright has expired and the work is now free for the public to use.This link from Cornell explains the public domain in depth. Essentially, anything published before 1923 is in the public domain and is free for the author to use. Other works published after that date have entered the public domain, but they are dealt with on a case by case basis.
Now here are some sources that will aid greatly in obtaining media for scalar: