Legal Question in Intellectual Property in Washington

Re: Internet Graphics

When asking whether or not a work would be considered fair use you must look at the four factors of fair use. They are:

the purpose and character of the use, including whether such use is of commercial nature or is for nonprofit educational purposes;

the nature of the copyrighted work;

amount and substantiality of the portion used in relation to the copyrighted work as a whole; and

the effect of the use upon the potential market for or value of the copyrighted work.

Applying that to what you've described, leaves me to believe that your work would not be fair use since it would fail under the first, third, and fourth factors. Your option would be to license the images from the NFL or legal owner. Just because images are available online does not mean that they are public domain, i.e., anyone can use them for any purpose.