If you need more than just a photo viewer with which to manage your images, you could have a look at Aoao Photo Editor.
This easy viewer not only lets you browse all the photos in your hard drive, but also includes a bunch of tools with which you can rename them, convert them from one format to another and perform some basic editing operations such as adjusting color and light, adding a watermark or drawing figures over a given photo.
Aoao Photo Editor is a handy application that includes the basic tools you need when dealing with your photo collection. However, the program fell short of our expectations. The interface needs a redesign that makes the program easier to use – and more visually appealing also.
Aoao Photo Editor has some confusing behaviors as well: for example, when you open a photo in full screen, there's no way to go back to the folder list without closing the program. Also, I miss the option to have auto-adjustments in the editing tools.
Aoao Photo Editor has more features than a simple photo viewer, but is still far from other similar apps with better appearance and more powerful tools.