Before Jabba the Hutt ended up being a giant slug in Return of the Jedi, he went through several other design iterations. He was played by a human in the original Star Wars movie, but was supposed to be replaced by a stop-motion creature, which can be seen in the concept art above. I've never seen that design until now. It's really weird looking at some of these other Jabba designs. Most of them I've already seen, but in case you haven't, I've included them below.
Jabba made his first appearance in the comic book adaptation of A New Hope looking like this:
These are some more concept drawings of the character:
Here's how Jabba originally looked in A New Hope:
And as you all know, here's how he ultimately looked:
Via: The Geek Twins