I would really like to show a symbol that looks like this one on my schedule. Is it possible?
You will need to add a custom symbol.
Save a picture you want to turn into a symbol as a bitmap (BMP). Be sure it is saved in the folder you have set (via Tools/Folders) for Symbols.
Double-click any unused symbol in your toolbox.
Click the User Defined Shapes drop down and select the BMP you saved in 1.
Click Embed Above Symbol in File. Then, even if the BMP is deleted, the symbol will still be kept in the Milestones file.