This is a good plugin to watermark your photo uploads with your brand but ONLY PHOTO ALBUM uploads because this plugin does not work on user avatar uploads. I have tested with SkaDate and it works fine. I found it very easy to install and set up. This plugin is excellent if your users are uploading a lot of photos you wish to prevent being re-used without due credit.
This is exactly what I was looking for, and about to have developed. It has several options, and is very customizable. I had some questions, and the developer was very quick to answer and also offer to add options that will make this plugin even better.