This looks really nice, reminds me of Muzei[1] on Android which also allowed to add effects on the image that was being displayed. Definitely keeping ArtDiario running! Just a little thing: consider making the icon for the menu bar smaller, it's way to big compared to the usual size of the icons on macOS and it makes it look off [2].
Muzei looks nice! Icon is a bit larger, was trying to get a good balance considering the letters are different sizes, but may adjust! Thanks for the feedback and for downloading!