If an ad fails to load, display "Thank you for playing my game!
that I poured my heart and soul into and the ad revenue I rely on to feed my 4 kids, put them through school, and support my mother in the hospital." instead.
Edit: Option 2 - "If you enjoyed playing this, check out my other games! - link"
If you can't fill the space up with monetized ad, might as well advertise something else.