Guin Saga is an epic fantasy novel series written by Kaoru Kurimoto. Spanning more than 100 volumes, the title character is a man with a mask (or head) of a leopard. It was made into an anime series earlier this year. Sadly, the author of the series passed away in May, leaving this massive story incomplete.
There isn't exactly an abundance of artwork for Guin Saga, which is a shame. This post has just about everything I could find from anime art and screenshots to what I believe to be novel illustrations.