The only thing I would wonder tho is if the NFL would have issue with you selling a players likeness. They seem kinda anal about that kind of stuff. Not sure of the law. You got major talent tho man...keep at it.
from what i have read, and searched for (but will still be contacting a lawyer for more insight), as an artist, what i create is my intellectual property. The subject of the artwork is me renditioning and my visual perception/creation. example being this painting i am creating, Russell Wilson is the subject of the painting and wherein he is wearing a uniform of the seahawks, and is a product of the NFL, I as the artist can paint that because it is coming from my creation.
if i take, and create a second, or third separate entity of a trademarked logo, on the piece of artwork, i am in violation of trademark infringement - example being if i took the Seahawks logo or the NFL shield and directly placed it in the lower corner (or wherever) by itself and not part of the subject depicted
as far as i have investigated, as an artist i have the right to paint/draw/photograph any subject as long as i do not falsely advertise or place copyrighted logos on it and sell my renditions as an artist.
but trust me, if this goes anywhere as i would like to see it go here shortly, i am and will be seeking definitive answers from a lawyer