Many users right-click on images as a way to download them (clicking the "save as.." option in the contextual menu). This is bad because users may get the scaled-down version which is used for display purposes and they are not given guidance on how to attribute.
We can use the HTML5 context menus feature to add some additional entries to the right click menu (Download original file, Get other sizes, view how to attribute...). The "Download original file" could have a download icon to make it more prominent than the standard "save as..".
This does not replace or interfere with the native content menu, but extends it on a standards-compliant way. Check more details and examples. Unfortunately, only Firefox supports this feature as of November 2014.