Like those meteorite coins! Additional world-ending events (for human civilization) could be biological pandemic, nanotechnology, killer AI, alien invasion, giant solar flare, global sea level rise, re-election of Labor and the return of Jesus.
A series commemorating the great ideas of Gina Rinehart, like the plan to use nukes for excavation in WA.
What about a Periodic Table of Elements 118 piece coin set. Each coin would have a tiny capsule with one element inside corresponding to each of the 118 elements embedded in the coin. .
Terror acts coin series. 9-11, PLO hijackings, Oklahoma City, Mumbai Hotel ... Or US Presidential assassins. Lee Harvey Oswald, John Wilks Booth, John Hinkly Jr.... No I got it, animals fighting, Bear vs Shark, Giraffe vs Kamodo Dragon, Eagle vs Chetland Pony!!!
Why? do they have a registered design for the lunars? as long as you don't fake it as legal tender they shouldn't have any problem.
Zodiac coins with the Chinese animal year on the reverse. A combination of 144 variations but only 24 dies. I'm Pisces in the year of the cat.
A planet series, with the sun being 1 oz AU. But then there would be an argument if Pluto should still be included as a planet. And I'm not sure I'd pay a premium for Uranus.
Keep the ideas coming guys. I will be putting a short list together this week or next then see what the community thinks , probably looking at 1k Mintage per coin if that.
Source: http://depositphotos.com/34136461/stock-illustration-all-possible-shapes-of-puzzle.html or Source: http://www.wikiart.org/en/m-c-escher/lizard-1