I get a lot of traffic, nearly half of my uv's per day from Google Image searches. I was just wondering if traffic from image searches was the same as from a normal search and will the popularity of my images be of value to my PR?
It depends upon what type of website you have, but many of those doing image searches are people looking for images to put on their own website
It makes perfect sense... they want images, you got them. If you want to protect them, watermark them. That way, no one will use them.
Your images will be of use to your PR if someone sees them and likes them then links back to your site. I've got a handful of links back to pages on my site where people have made mention on their site about an image. The people who steal your images don't help your site much. Image traffic has a much higher bounce rate than the keyword traffic on my sites so I'm sure people are coming to the site and downloading the picture. However, about 25% of the image traffic looks at other pages so I figure it's worth the trade for me. If you've got analytics on your site you can filter your referral traffic to sites containing "images" in the domain then compare the bounce rate to other referring sites or to your organic traffic to see if your image traffic is worthwhile.