Hello! Pretty hens! Hens usually start laying at anywhere from 17 to 25 weeks. I'm not sure how old your girls are, but they do look mature enough. One sure sign that laying will begin in about a week or so is the squat. When you reach out to the girls to pet them, they will do this really hard squatting pose.
Here's what I would suggest. If they're not squatting yet, take out the nesting box and wait until they start squatting to put it back in. See, if the nest box is in there too early, sometimes the young hens like to sleep in it, thus pooping in it. Bad habit.
So if you re-introduce that nesting box when they feel ready to lay, then they'll get the hint and root around in there, showing interest in the nest box, and one day, TA-DAAAAH! You'll find an egg there.
And pine shavings are just fine for the nesting box. I've never used fake eggs or golf balls, but I'm sure it won't hurt if you want to. Probably a good idea.
Take care and don't forget to post a pic of your first egg! It's so exciting!
Sharon