I'm not sure what the industry-standard term is for this view. In Adobe Lightroom, this is called the "photo grid" (as opposed to the "square grid").
This UI is used by several modern photo viewers, but none have the performance and flexibility of XnView. Thanks for all the amazing features you've built into XnView!
Microsoft Photos

Adobe Lightroom


Pictureflect Photo Viewer

PhotoInsight

Google Photos

123 Photo Viewer

Pinterest-style Grid Layout
