I use Flickr and you have to grab the actual static url and not the link they try to get you to use.
This is what Flickr tries to get you to use "
IMG_2344 by manical modeler, on Flickr"
But you reall want just the portion that precedes the ".jpg"
It will look like this, but without the spaces I've added to make it appear like regular text: https: //live.staticflickr.com/65535/50055043437_4e8b40dbe4_k.jpg
So inserted, that url will look like this: