One big drawback of wordpress as a content management system is the way it deals with various image sizes : when you upload an image to the wordpress media interface, your favorite CMS software creates thumbnails, medium and a variable occurence of intermediate image sizes, depending on your main theme and installed plugins. For example, Woocommerce is a top plugin and it creates three intermediate images. It is good if you have all plugins prepared and installed before working on images and content, but if you need to make changes to layout or front end display requiring specific or new image sizes, you have no other options than going into the code, declaring that new image size, and use one of the numerous plugins that allow you to regenerate all images for that specific size you've just created. Apart from the fact that it is not a very funny operation, it also creates images for all media files you've ever uploaded including the ones that will never need to be resized to the new size. And if you don't regenerate the images you need to display, well they simply won't work.So as a result if you have been working on your website for years and trying out dozens of different image sizes, they will all be stored on your hard disk, and that's size intensive and slows down your staging / backup / restore operations that are a minimum for each serious site
Well that's one solution, and the other solution is to use dynamically generated images. Some plugins do that, and hopefully one of them combines the best of both world : fly images resizer allows you to create new images sizes that will be cached to a specific directory that can be cleaned if you need to. I'm just after testing the plugin and it comes with the same kind of feature that wordpress has imagined : creating new image sizes including crop option, registering those sizes or in code dynamic image size creation. It has a small back end link that allows you to delete cache, and one improvment I suggest would be to allow specific image size cleaning.