All righty, I reckon it's time for me to start a new world for the latest update (I've got so many worlds now, heh - I tend to start a new world every time Mojang releases a new update, in addition to the random seeds I like to try out).
Edit: You may already have noticed this, but there's a new skin in the mob folder:
It's titled "silverfish.png." It's not in the game yet - the skin has just been added as a teaser for now, so I'd say it's likely to be a new mob for 1.8. Now, it could be a silver-coloured fish, or an insect silverfish:
If it is indeed the insect rather than the fish, that could have some potentially interesting gameplay consequences. You see, silverfish are known for being household nuisances, due to their tendency to destroy paper and wood-based materials...