Straw to scratch through. Shade. Roosts. Places to not see everyone- so, a little clutter to block sight lines.
Put their water in a new place- wow, exciting!
Make a wet mash if their feed, sprinkle some marigold petals or seeds or scratch on top -chicken nirvana, and they are still eating their feed!
Things that make them play chase: one blueberry tossed into the run, see them run, then chase the one that got it! Off they go in another direction! Another one stole it, there they go again! Repeat several times.
Unbreakable mirror : they see new chickens!!! What!! They peck, they look, they talk.
Black dots on the wall- it looks like a bug!! They peck and peck!