TinyMCE 4 and 5 plugin Flickr image search
Search for flickr images, see a preview and insert into the tinyMCE 4/5 WYSIWYG editor
You can select some params like title (alt tag), size, align right or left or open larger image with a lightbox
A great way for editors to quickly insert images into content pages.
Only thing you need is a developer key from Flickr (yahoo) and read all about the licenses. NOT all images can be used for free on (commercial) websites
A demo can be found here