Feather is a collection of simply beautiful open source icons. Each icon is designed on a 24x24 grid with an emphasis on simplicity, consistency and readability.
unDraw is a constantly updated collection of beautiful svg images that you can use completely free and without attribution.
Beautiful images for your client and personal design projects, without attribution. A completely different kind of plugin, exclusively on XD.
DottyDots is a Dotted icon style that Icons8 team created for their icon library where users can not only download icons they like but add overlays or recolor icons in just a few clicks.