If you have a project management tree,to visually distinguish the different categories. The simplest way I’ve found of doing this, is to use http://copypastecharacter.com.
Just visit the site, click the character you want, and paste it into your card.
I know there are better and prettier icon collections, but if the idea is to quickly put something in there, and move on, this has been my choice so far. Our favorite set CopyPasteCharacter.com