This would me more interesting and more people would participate if you also posted bits of modern coins.
I myself don't collect modern coins so I'll just be posting ancients/medieval when I win, but if anyone else that wins would like to post a modern world coin, I wouldn't mind.
There is absolutely nothing that would prevent a separate thread supported by modern collectors along the lines you suggest. I would think it better to keep the two separate since the number of people who are active in both is not high. I doubt we could even agree on what is a modern coin. To me, this would start around 1500.