An arty brain

This is a neuron, done with a colourful watercolour like flare. It's pretty vibrant.

It does look like a neuron, but it wouldn't have come to mind if I hadn't have known. Looks cool anyway.

[Source]

Painter of the skin

This work by Amanda Wachob is pretty cool, and there's plenty more on her site.

check it out here.

One more under the jump

Pretty darn cool

I though these were pretty awesome, these are by Peter Aurisch.

You can find more work of his here and here 

and there's plenty of other awesomeness