Image extract v2.0
This add on looks over the body of a webpage and then removes everything that isn't an image so you can see the images on a page more easily.
Easily combine with Firefox's inbuilt screenshot tool for basic cropping or editing.
Source, issues: https://github.com/Skeletonxf/image-extract.
If you find a (publicly available) webpage where this addon cannot detect an image visibly on screen at the time of running it please writeup an issue on the GitHub repository as a bug.
Image Extract's keyboard shortcuts are disabled by default so you do not accidentally trigger them.