Please don't use AI-generated assets as placeholders! It makes your work look scummy and cheap, as if you don't plan on putting that much effort into it. Besides, there are alternatives that creators have been using long before AI was an "option".
You can use real stock photos or silhouettes or sketches with the word "WIP" on it. It's still just as efficient for creators on a budget and time constraints and it will put you in a much more favourable position.
Sorry if this comes off as rude or confrontational! There's just no other way to say this.