Never heard of Heroicons before (looks like they're made by the same company that makes the other products listed on the website.)

But I've used FontAwesome before which I believe (or hope) is still the industry standard for free icons: https://fontawesome.com/ . Not sure if Heroicons or something else has displaced it in popularity rankings.

The other products -- Unsplash for photos, Undraw for illustrations -- were pretty cool references though and I'll be bookmarking them. Does anyone know if there are other resources for photos & illustrations that are popular among web developers?