I personally use Irfanview as my default image viewer. It's tiny, uses very little in the way of resources, and its basic interface hides TONS of cool features. I use this for general image viewing, as well as when I want to batch convert or rename a bunch of images.
IrfanView is a very fast, small, compact and innovative graphic viewer for Windows. It is designed to be simple for beginners and powerful for professionals.
IrfanView seeks to create unique, new and interesting features, unlike some other graphic viewers, whose whole "creativity" is based on feature cloning, stealing of ideas and whole dialogs from ACDSee and/or IrfanView! (for example: XnView has been stealing/cloning features and whole dialogs from IrfanView, for 10+ years).
Configure a custom computer with the Irfanview.