What makes Animation Art valuable?

Age and rareity are two important factors. What character(s) are in the Artwork, and what expressions they are showing. Figures in a full pose position are normally more sought after than a head shot or half body pose. Memorable scenes from classic films or cartoons create a high value. Villains and Princesses are also valuable. Signatures of artists connected with a specific production can often increase the value. Walt Disney's signature on the mount/mat will also increase the value, as he never signed the artwork itself.