http://divshot.github.io/geo-bootstrap/ (via https://news.ycombinator.com/item?id=5508061 and https://news.ycombinator.com/item?id=5474022)
Also http://www.geocities.com/clipart/pbi/backgrounds/ (not exactly what you asked for, but... interesting that it's still up there) (found here: https://news.ycombinator.com/item?id=5919862)