Flickr should have a choice of disabling the picture to be opened in a new tab or window and right clicked and downloaded.
How about a feature that disables opening a picture in a new tab where it can be right clicked and downloaded.
Niko Hörkkö commented
That's not possible. If the browser can display your image then it can be downloaded. If you're so afraid of people downloading your photos, don't post them online. That's the only 100% safe way of making sure people don't download them.