Can we get the ability to watermark multiple files in one go?

I use Dropbox not only to deliver final images, but to show multiple lo-res images beforehand for selection purposes.  Sometimes hundreds of images in the form of a "library", I like to allow clients to download them for ease of selecting and for future reference.  Since I don't want images used that might not be "ready for Prime Time", or published without permission, they need to be watermarked.  The Dropbox watermark feature works fine for one image at a time (great that one can remove it, too), but it would be a huge time saver if images could be batch watermarked.  An additional feature with batch watermarking would be to enable editing of individual watermarks within a batch; sometimes a repositioning is needed for clarity.  While I have someone's ear, having the ability to add a custom watermark would also be brilliant. 

Thanks!