You're following a very common route for this slime, it looks like pretty much every other 'slime' creature you see in anime-esque roleplaying games to me. What you need to ask yourself is what can you do differently? If you're not interested in that you'll practically be creating fanart. Just a thought.
Check this reference out:
http://www.fotosearch.com/UNZ221/u12261348/Now imagine that jiggling, you could have a really nice effect with the reflections. At the moment your slime is more like a rubber ball in the way it's rendered. Highly reflective surfaces have strong highlights! But i would advise against going down Jad's route, since his is very stylised and you will really be lacking much original input.
I don't think the 'angry cross' symbol works as a physical construct. It's an emotive shape to signify an expression, like an exclamation mark to emphasise surprise, therefore i would remove the highlights by it. Now i realise it's based upon a bulging vein idea, but i think you could get a better result by creating a bulging vein without the common symbol in mind.
Finally, you could use more dark tones when shaping the facial features instead of blacks - at the moment the features look like they're cut into the blob. Even though it's quite cartoony i think it could benefit from some more depth and structure.