You used to be able to do this by clicking on the image in "Edit Media" and then clicking on the "Advanced Settings" and clicking a box for Target - Open in a New Window. But I don't see this feature w/ the new WP update that changed image handling. I think it can be done for
galleries using NextGen Gallery plugin.
The coding issue would be that the images set in each post are specific content to each post as far as how I understand WP. So maybe Fris or someone else can advise you the code to insert to loop thru the posts, use regex to grab the images and code them to open t\ blank ???
