Definition of "illo"

We will also begin paying for art work: about $20 to $35 for a full-page illo, and others in proportion.

1981, George H. Scithers, Amra, volume 2, number 69, page 9

[…] this 188-page photo/illo tome is a gorgeously provocative companion piece for music heads consumed with the classic and the current.

2008, Vibe (November 2008): "Idol Worship" by Keith Murphy