So depending on monitor resolution and scaling, tray icons on Windows can be 16px, 20px, 24px, 28px or 32px. On my monitor, they appear as 20px, so the 16x16 Insync icon appears extremely blurry:
I recently learned a way to manually make ICOs of multiple sizes, by following this tutorial: https://medium.com/@JonGraft/using-adobe-photoshop-or-illustrator-to-create-an-ico-82e573279f6b
The tutorial template doesn’t include a 20x20px version, though, so I added it to my copy of the template: https://puu.sh/GO4Sx/30e64120a9.psd
Having sharp tray icons would be very nice.