Pocket - When you find something you want to view later, put it in Pocket.
Imagus - The extension is intended to complement image features that (I think) is missing from Opera by...
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Image Max URL - Help find larger or original versions of images, including a customizable image popup feature
wallabag - Save the web, freely.
Thumbnail Zoom Plus - The official site of the Thumbnail Zoom Plus add-on for Firefox