Omake

From The Heretic Knowledge Vault

Term for "bonus" material going beyond the bounds that a product normally promises. The term is derived from the Japanese; for a full explanation, check this Wikipedia article.

Filler art generally qualifies as omake, and the recurring Fun with Familiars series is definitely omake. In addition, images of Miyo Hinadori (the one used to illustrate her article) and Riley (lost for the moment -- warning, definitely not work-safe) have appeared as omake previously. There'll be more.