1. You can set the thumbnail size to anything you wish. 75X75 is the default one, change it to something bigger if you wish.2. The uploaded images are not lost. They become the full-width images. It is very bad method to resize the images on-the-fly each time someone wants to see them as you push the server's CPU to its limits. The most wise solution is to resize them at the wanted size at the time you upload them.3. It is easy to add an automatic re-size. If this is your problem it can be done.4. Watermark can also be easily added.I believe that you worry too much. You could re-size your images before upload to the desired width X height.