Trigraphy - Photo editing app that allows you to make mosaic/abstract looking art.
Meazure - What are the dimensions of that image? How big is this window?
Dreamscope - Make and share 'deep dream' images using dozens of supplied styles or your own.
Bluegrams Screen Ruler - A lightweight and configurable ruler tool for Windows Desktop.
Photomosh - Turn anything into a vaporwave
ScreenRuler - ScreenRuler lets you measure objects on your Ubuntu desktop using six different metrics.