ronnie,
What is it that you want to protect your images from?
If you look at it from SE's POV it could be seen as
cloaking. Different content is served.
Both images and text is copyrighted. But we still let them spider the text, so we can get hits. We also let them spider our images, so we can get hits. Maybe not as productive traffic, but that's our POV.
Spiders doesn't only spider regular html pages anymore. Images, videos, PDF, Power Point presentations, you name it.
Some doesn't like getting their PDF's spidered and some doesn't like their images spidered, but from SE's POV I don't think they appreciate that all hits to the document is redirected elsewhere. But from our POV, it's good. We can get more traffic to somewhere else. But it's the same thing as redirecting all traffic going to HTML pages, it's just a different media.
SaucyPanties,
Just send me a PM with your URL(s) and I'll take a look at it.