Sprucing up new outdoor enclosure

I don't like to have grass in enclosures where the animals inside don't eat the grass, because that means eventually the human will have to cut the grass, and because of the size and shape of enclosures, this mean hands and knees and scissors.

That's looking good! I agree with Yvonne too.

Mine love to climb the logs, bark and rocks. One good thing about turtles is they don't have issues flipping upright, (at least mine don't). I've always added plenty of furniture to my enclosures for hiding and just for them to stay active. I think you're on the right track with this enclosure though!!

I would leave a little grass, but I would make a majority of it with dirt. And then dumping a bunch of leaves etc. And throw in a bunch of different things for them to climb on and hide under like rocks and bark and branches etc.

And if you can't get leaves at this time of year, get some sphagnum moss and pile it into a couple of areas, lightly wet it down. They just like to burrow under stuff.
I have some slightly arched branches that form sort of a small 'shelter' in one area of mine. I zip tied them together. I added leave underneath. Mine love this area to burrow into and watch for bugs.

Broken flowerpots make good hides. Check the side of the road on garbage day in the spring & fall if you haven't broken your own.

My experience with grass is that the turtles bulldoze it or burrow under it, and it doesn't require mowing in the end.

Look at it as an experiment to see what works for you. I can say that turtles do respond to positive changes in their environment.