Since yEd supports popular image formats JPG and PNG as well as the popular SVG vector graphics format, you may import icons from most icon collections available online. See How can I use my own node symbols in yEd? for details on importing icons into yEd. (yEd even comes with built-in support for accessing Icon Finder, one of the many online icon collections.)
There are even Github projects for ready-to-import yEd palette sections such as yed-fa-palettes.