-Dog size spiders: When they walk their legs would connect with walls and floors. I think that would be so cool/terrifying.
There could be 'nests' in forests or caves that would have sticky webs to catch you, and lots of little spiders.
-Some sort of stalking goblin/Gollum cave creature (half your size?) that would be very stealthy, and would be attracted to lights underground: stalks you in the dark.
-Monstrous worms (3x your size?) that would live deep down in specially generated 'maze burrows' that they would patrol.
-trapdoor spiders/scorpions that would wait in caves for prey. Poison you?
Just my wishful thinking. I've been mining a lot, and look forward to having some dangerous encounters down in the depths.
Thanks again for all the hard work put into this beautiful game. I never thought I'd love a stone texture, but it really feels like i'm underground. Very claustrophobic. Well done. 
