The scene in the 1977 comic book adaptation :
Yeah, they used this background alien. Presumably from the stack of photos they got from the studio. He remained Jabba well into 1980. I don’t think Jabba appeared in the comic at all between ESB and the ROTJ adaptation. The quest for Han obviously couldn’t succeed in that period.
You can also spot him in the Cantina trying to drink. Not sure if he was supposed to be drunk or the actor just couldn’t see well enough to get the glass to the lips on the mask. 😉