Yo Skeddles!

You can fix that slime shape! It's more gel than slime, but also it has a corner in the top left, a corner in the base plate, and overall doesn't read very soft and squishy. It gets softer if it would get slightly wider at the base, being hardly able to support it's own weight. 
The base thing suggests a slightly top down view, yet the face suggests a side view...

Maybe draw a couple slime monsters by hand on paper to figure out how a smooth slime should look and behave?

What's with the star highlight on the slime? A single sparkle? Texture is smooth and soft, not with extreme point highlights!

The inner AA on the lineart has a weird effect on the line thickness. Correct this by making the line thicker on the non AA part or thinner on the AA parts.

And I suppose the background and the text isn't finished yet?

dragon is coming out a lot better

replaced slime with imp:
/

finished dragon:

nice dragon and imp i think you should make what you wanted firstplace tho
try untill you got it this way you will not have problem with slime next time this is how you learn different things at the end you will be self confident that you can make almost anything you want