One of the things we are excited about with expression engine is that watermarking images when uploading is so easy for admins. Unfortunately we have also discovered that files can only be uploaded one at a time. I know that there are plugins that can manage batch uploading but does anyone know if any of them also offer a watermarking feature as well?
Channel Images can do that and a lot of other neat stuff: http://www.devdemon.com/documentation/channel-images
The CE Image plugin has a watermark functionality (and much more), check 'watermark' on this page: http://www.causingeffect.com/software/expressionengine/ce-image/user-guide/parameters