Yes, even the toy catalogs had them blurred out. Jabba was blurred out too.
I think the only ROTJ character to get any official exposure before the movie came out was Admiral Ackbar. He was Kenner mail away figure at the time.
The Marvel comic introduced a bunch of ferocious little furry creatures who help the rebels about a year or so before the movie. Lucasfilm requested they be redrawn to avoid similarities with the Ewoks.