At last a question with a short answer. Are your images an important part of your business? Are they driving traffic? Obviously, I would redirect all brand assets such as logos, product imagery etc. but the stock photo you use as your hero image, maybe not. If the images are of value, then redirect them if you are using the same image on the new site. If your business is selling images, redirect all of them. If people are linking to your images, identify why.
If the BBC is talking about you and have hotlinked to an image directly, I would preserve that image on its original URL if I could, otherwise I would redirect it.
If some dodgy scraper blog was hotlinking to my images I would redirect those images to an image that expressed my distain for the blog in question using some custom rules.
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