I appreciate the artistic feedback. We have considered an update to our icon library, but since it can be manually updated/customized by individual users, this is a lower priority update. I recently purchased a new library from Nucleo in addition to adding my own, custom icons over the years. You can create your own sub folder in the icon directory to be used in TheBrain.
Windows: C:\Users\[User Name]\AppData\Local\TheBrain
macOS: Macintosh HD/Users/[user name]/.TheBrain/v9/
and open the Icons folder.
You can also click on Help > Open Log Directory in the desktop app and then move UP one folder level to locate the Icons folder.
Create your own "Favorites" folder and drop in any image files you would like to use as icons. We suggest using 48 x48 pixel PNG files.