Faststone Image Viewer is a great little free app that I have been using for some time to view and organize images. One great feature is that it renders RAW files and it does so very quickly. It seems every time I need a quick solution for an image related challenge I find it has a function to handle it. The batch process engine handles resizing of multiple files very quickly, and the latest challenge of resorting images based on time (shooting with two bodies) and renaming the files sequentially was done effortlessly. Give it a try and see if you like it.