This can be easily implemented by adding a file attribute with a page selector attribute type. If you then override the view.php, you can use the link that's connected with the image.

Wow, fastest support ever...! :)

Thanks for the info! But that would mean that i would have to add a file attribute to each image of the chosen file set? And - wouldn't that interfer with the functionality of galleries (like Grid Gallery 2 for example)?

That won't interfere. You can create the file attribute yourself and name it like you want of course... (e.g. random_image_link)

I'd say that every image has a different link, so yes, you have to set the link for every image. If the link is the same for each image, I'd just create a custom template and put an a-tag around the image...

Thank you so much, that helped my a lot!

Unfortunately i got stuck with trying to insert the file attribute (link) into view.php.
I have created file attributes for all images of a certain set. Now i wonder how i can call them in custom view.php as a href="..."
May i please ask you for help one more time...?

Something like this:

<a href="<php echo $fv->getAttribute('random_image_link') ?>">img</a>

Thank you, it works perfectly now!