Material Design Icons
TouchDesigner includes the "Material Design Icons" font which can be used to create nice looking icons in places where normally text will go. Any label parameter will take unicode strings as long as the selected font supports the unicode codes.
Using Material Design Iconsedit
To pick and icon scoll through the list of icons on the Material Design Icons Cheat Sheet. TouchDesigner 2020.40000 series of builds ships with version 5.3.45 of the Material Design Icons. The cheat sheet is located here: https://pictogrammers.github.io/@mdi/font/5.3.45/ - The icon font library is often updated so make sure you are using the correct cheatsheet for the version included. Newer versions will contain icons not available in older versions, and may also replace some icons. (For TouchDesigner 2020.20000 cheatsheet, go to https://pictogrammers.github.io/@mdi/font/3.3.92/)
Click the HexCode beside each icon thumbnail and it will copy the hexidecimal string to the copy buffer. The string that is copied is just a hexidecimal index number but it must be made into a python compatible hexidecimal format by presceding the regular string with a '0x'. For example, if the hex code that was copied is 'F0EF4' the python hexidecimal notation is 0xF0EF4. Therefore, in TouchDesigner paste the hexidecimal string code into an expression of the format...
or more specifically in the case of 'F0EF4'