If you go to Google Images and search on a keyword, and then click on new SafeSearch filter drop down (might only work on a PC), you will see a new way of reporting offensive images. A drop down lets you select, “report offensive images.” Here is a picture:
When you click it, the page changes, to give you check boxes and a way to report several images as offensive. Here is a picture of that page:
This does help people report several images at once. It does not seem to work for me on any Mac browser.