It was drawn by Duane Bibby, a well-known commercial artist. He used this lion in the illustrations for D Knuth's original TeXbook, for L Lamport's LaTeX book, and for other books having to do with TeX, so his work is familiar to everyone in the community. Because of that, his beautiful and insightful drawings have also graced TeX conference posters, tee shirts, and coffee mugs.
He generously made this artwork specifically for us. We love it, in part because it is ambiguous; the lion could be a user referencing the material that has been made available but he could also be a dedicated archivist working late into the night, slaving tirelessly, to place those materials out for public use.
You can use this drawing if you like, either personally as on a login screen or publically as on a web page. For public uses we would appreciate an acknowledgement such as "CTAN lion drawing by Duane Bibby; thanks to www.ctan.org". You can get high resolution versions in case you have the eye to touch up the scans.