It may sound trivial, yet it’s the most frequently made mistake with images:
▪Don’t add an image to a document only because you think it “looks better” to have an image there. And even if it actually does look nice: If the image has no other purpose than being beautiful, it just stands in the way of the users.
▪Don’t add an image only because you feel that you need any particular number of images. If your document or parts of your document don’t need many images, this is fine.
▪Optimize each image for exactly one purpose.