Based on the thousands of slimes I've killed ( ), I would say the first thing you should do is get rid of the dithering--slimes are smooth, and in the piece, the dithering makes it look fuzzy and textured.
Next, I think the translucency could use some work--you can usually see through a slime--although I guess there are occasions where they are more of a matte gel...
And, lastly, if it where mine, I'd lose the black outline...but that's just me; stay with it if you like it man.

Good luck with this.  Oh, and I have to ask; are you just redoing just this sprite or are you going to overhaul the whole game? because that'd be very interested to see. 

it might just be me but i think this sprite is just too small to tell that its a pirate.  It just looks like a guy wearing a bandana on his head.  Maybe it could be a bit bigger or give it some defined pirate features like a striped pirate shirt or a hook hand.