Come on, it should really be common knowledge by now that there is now way to prevent downloading of images from a website except not uploading images to a website in the first place.
You can disable the right click via Javascript but if someone disables that it will work again. If you view an image on a website it has already been downloaded to the browser cache. If someone wants it he gets in anyway (and if it is just by creating a screenshot..).
We will not implement something like that.