I made a new minimal icon for the fantastic Lyx document processor. Here’s the 512×512 icon Lyx icon suitable for using on MacOS (and probably other OSes); and here’s the Lyx icon SVG source.
On MacOS, you can replace the default icon by doing “Get Info” on the application file, copying the image from Preview, then pasting it into the icon square in the top left corner of the Get Info window.