OK let me dump my ideas first to catch some eyes
More trolls like volcanic trolls or even frost trolls for the deepnorth
more dragons even dragon taming for end game flying
lava creatures
obsidian armour and weapons with enchantments maybe
new volcano and boss with surtr the fire giant of Norse mythology

these are just a few of many ideas i have for future updates ie ocean and deepnorth but i want to keep this small for now (: