Well, got all of them now. It was the one behind the orc chief's hut that was missing - I just hadn't realized there is a space there. Though I needed to use a bit of console magic to find it. Here's...

Got all of those. I'm probably missing some relatively simple one that cannot easily be seen from above (I can use a cheat to float high above ground to get a better view, but still nothing). Might...

Which waterfall is that?

There is one big waterfall near the Orc village and the bridge, but there's no artifact there (and no trees either). There's a forked waterfall in the elf forest, where...