UFO FREEBIES #ERROR 404
Cute illustration. Also available in @2x PSD over at the Dribbble page.
UFO FREEBIES #ERROR 404 is a free Template design resource made by Dribbble user Brice Séraphin. As far as I can tell, its license is Unknown.
Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.