Quixel library is HUGE. Contains tons of very high quality assets.
Found this by typing "road sign"
Discover a world of unbounded creativity. Explore a massive asset library, and Quixel’s powerful tools, plus free in-depth tutorials and resources.
quixel.com
There is also rubble, planks, trash, bricks and all that stuff.
The cliff side from junkyard level.
You can match and mix anything. The assets are very good because the cliff asset can be enlarged to be a mountain. It is so detailed.
You can see on min 5 how you can move and rotate assets and create whole landscapes from that.
I don't know how expensive it is but game dev must've gotten so much easier with it.