The program supports JPEG, Bitmap, GIF, PNG, TIFF, ICO, WMF, EMF. Although if GIF images are animated GIFs it only shows the first frame.
NexusImage doesn't need to be installed and it runs really well. Run the program and choose the folder you want to explore. You'll get a list of thumbnails in the sidebar.
Although the functions of NexusImage are very limited, it offers a different way to view images and it can suit your needs with no problem.