If you block crawling/indexing/whatever your images you need to think about Googles "preview" function.
Block G from images and your pages are going to look like the site is abandoned in the preview view. Been there, done that, bad news. Logos, product images, info images you name the image, or image type, how will your page look without them?
Would you click through to a page where all the images were obviously missing? Bye, bye human traffic....!
At the very least, consider putting a little smaller and/or lower quality image on the page, and make that image clickable leading to a better/larger image in a restricted directory.