Currently Unicode chars works in From name and in the Subject Line
Unicode chars can be inserted currently via copy/paste
Here are examples of Unicode pictographs:
https://unicode-table.com/en/sets/flowers-symbols/
https://unicode-table.com/en/sets/emoji/
https://unicode-table.com/en/blocks/miscellaneous-symbols-and-pictographs/
https://unicode-table.com/en/blocks/miscellaneous-symbols/