HAH! I remember those, my brother had the whole series in two giant-format books, they were great!
I keep telling people about the slim, humanoid Jabba, but hardly anyone believes me. Nice to see I wasn't imagining the whole thing. If I remember right, someone told me that when they made the comic Lucas hadn't finalized the design for Jabba, so the one that shows up here was just a placeholder of sorts. But that might not be right, it'd be nice if someone could confirm that somehow.