I think the best advice for me was "Add sample data to avoid an empty nest." I just realized that my product has this problem, so I'm going to be adding some sample data for new users. I think I'll also have a toggle switch so you can easily hide all the samples. (It would be annoying if you had manually delete everything.)
Concierge setup is also a great idea, and I've recently been offering that to new customers.
So instead of "0 photos" and a blank page, it could say "Get started by [uploading some photos]".
I really like this approach because the use case for products like these varies from one client to another. Just throwing in some demo data that's always the same wouldn't really help everyone.
What users actually want is a quick way to work with their own data.
A specialized "first launch wizard" that makes entering inital data really quick and painless is often a better choice.
It can also make sense to allow trying the product out with existing data, but for this I would offer a "demo" mode where you get bootstrap data, can play around with it, and have a big banner on top that allows launching the real thing.
This depends on the product of course, but I prefer those two options above.
I respectfully disagree with that view and I say that as someone who has implemented a product with sample data during the onboarding process.
Users don't care about your data. They care about their data. The easier you make it for the user to input their own data and get some value out of it...even if its something trivial...the faster they'll be able to relate their problem to your products ability to solve it.
In general though: most onboarding I've disliked, too slow, but some with "click here to do this, or elsewhere to end the tutorial" have been good.