Treats are nice. Old corn cobs, cantaloupe innards for the full-grown hens. Leftover spaghetti, red cabbage cut in slivers. A fresh sprinkling of the neighbor's hay. Sunflower seeds in the winter. Yes, they love tomatoes.
We had an elderberry tree in our old coop (and soon in our new one) and it was hilarious to see them leap to great heights flapping their wings to get at them. We'd toss in a few from the higher branches. Goumi bush--same thing. Fence off the young plants, because chickens love elderberry leaves just as much as our local deer.
Old stumps, yes. We are learning what good tillers they are in their new day pen-- lots of stumps to dig around, jump up on, hide behind.
Places high (well, not too high) and low. A bale of hay or straw for them to hop up on or hide behind (we have a scaredy pullet right now and I'm learning about the need for hiding places.) They like little perches in the sun where they can groom themselves. A little tree if you are not concerned about them getting out or daytime predators getting in. (We use a deep litter mulch "system". A bare yard might just kill trees and shrubs planted there.) I feel sorry for flocks stuck in bare, level, featureless yards. Even just sticking in a few pots of bamboo in the middle and an extra perch or two is enough to provide a bit of interest.
In our new, larger day pen we've put in an extra covered spot that we layed hay under, a second waterer next to. Good for sudden rains, predators, shade, and jumping on top of.
If you have enough space, divide it and rotate. They will be thrilled for days and days.
Pulling back the old mulch to harvest is worm-hunting time. We once had a hen (it makes me want to cry to say that) who spent so much time pecking and getting angry at the others for eating "her" worms that she hardly ever actually ate the worms.
The girls (the human kind) would like shelling old, starchy peas to hand feed them.