Ohh. Yeah, that's not an easy decision. You want to grab people with a cliffhanger, but if it's placeholder art then some people could be turned off by that. Although I think only a small amount would turn their noses off, especially when you make it clear that you want to give the people a deeper look into the story, but it's placeholder art for now that will get replaced in the future.
Does itch.io allow different releases? Like an additional demo-beta release?