The largest in game surprise is the question of the day and I really have no clue on this one. So here I will distract you with something shiney.
A game I am looking at starting is a hexcrawl (at least if my son is still getting freaked out by the foreshadowing in Princes of the Apocalypse, otherwise we shall continue that one). Besides the monsters in the Monster Manual I have adapted some based on Japanese Yokai, my Beta document is Here (web page best viewed by Chrome Canary). When I have a more complete beta I will add a few pictures from the public domain and generate a PDF.