"Nothing" images
It's like with the two little rovers before. There were loads of weird images, blank ones of the sky, shots of a bolt or something, stuff like that. All of them had a reason behind them (sky brightness, calibrating something, checking dust accumulation on a part, that kind of thing.)
My wife had to train me to use a digital camera. I still had the "wasting a picture" mindset from decades of film.
"See this camera?" she'd say. "How many pictures are left on it?"
"Um...5,000."
"Right. Now shut up and take a bunch more pictures."