I ran into a couple of minor problems while trying to test qView. Firstly, I couldn't download it from the homepage with either SeaMonkey or portable Aurora; I managed to get it from the Github repository at https://github.com/jurplel/qView/.
Then, when I tried launching it by runing the single executable, it complained about lack of 'msvcp140.dll' and 'vcruntime140.dll' libraries. I managed to get those files from the latest Firefox folder and after copying them over, qView launched without any further whining.
One further annoyance I encountered was, while it ran in full screen alright and I found I could use the Escape key to exit full-screen, I was unable to find any way -- no Escape, nor any menu option -- to quit qView, apart from clicking the Windows close button in the top right corner.
qView: an image viewer for viewing. No toolbars or distractions -- pure space efficiency.
qView 32 or 64-bit "portable" version (currently v2.0) can be downloaded from https://github.com/jurplel/qView/releases.