If you look on the images tab there is a link to enable our image protection. All that does is stop people from right clicking to save them. Someone who really wants them can use other methods to get the photo still.
There is no real way to stop people. You could create a custom template and do like you said which is to create a transparent photo across each place we put in a real one. That's one of the better ways actually. I wonder why we don't do that?
The other really good way is to watermark your photos before uploading them.
We'll be adding watermarking in a future release so it happens automatically when you upload your photos. Maybe we'll also do the transparent thing. All that does is slow them down. A person could still go through the media tab in Firefox for example and get the image under the transparent. That also gets them around the right click protection we have.
