As a developer, I appreciate feedback as soon as possible. I'd rather get suggestions/feedback/defects/bugs that I've already addressed than hearing at the end: "I figured you'd fix that."
You see it, you don't like it, report it.
Make no assumptions, what you see now can very well be what you get in the end. Don't assume anything more than what has been delivered or described. They were made this way for a reason: either as a placeholder, or a style, or as something to generate feedback.
Just keep it positive, maybe it IS intended to be this way. Give suggestions on "their best work so far" and you can't go wrong.