Viewnior is described as 'Very simple and fast image viewer. No support for IPTC metadata such as image tags/keywords' and is an app in the Photos & Graphics category. There are more than 25 alternatives to Viewnior for a variety of platforms, including Windows, Linux, Mac, Xfce and PortableApps.com. The best alternative is IrfanView. It's not free, so if you're looking for a free alternative, you could try nomacs or ImageGlass. Other great apps like Viewnior are XnView MP (Free Personal), XnView (Free Personal), JPEGView (Free, Open Source) and Preview (Free).
nomacs is a small, fast image viewer able to handle the most common image formats including RAW images. Additionally it is possible to synchronize multiple viewers. A synchronization of viewers running on the same computer or via LAN is possible.
ImageGlass is a simple picture viewer with which you will be able to display your image collection in a very similar way to the one that Windows provides by default, but with some additional functions.
Imagine is an Image & Animation Viewer for Windows with screen capture function. Features - View and save image/animation files with very fast speed - Support for numerous image/animation file formats: GIF, BMP, PNG, JPG, TIF, TGA, PCX, ICO, ANI, FLI, and many more...
Eye of GNOME is the official image viewer for the GNOME Desktop environment. With it, you can view single image files, as well as large image collections. The Eye of GNOME supports a variety of image file formats.