The first few designs were not bad, but, I'm glad they stuck with their final designs. Take a look at Andrew Baker's stunning detailed monster concept art from [The Hobbit: The Desolation of Smaug](movie:512310). From the grotesque Orcs and Beorn in his gigantic bear form to the demonic spiders of Mirkwood.
I give to you Andrew Baker's beasts of The Hobbit!
Beorn in bear form:
The giant spiders of Mirkwood: