In addition to what @teefers says, there are also problems securing signed photography release forms from the original photographer or models. Especially any photographs you decide to use that contain faces or branding. Unfortunately word of mouth, a 1-line email or a quick screen grab would not satisfy anybody in the legal profession tasked with resolving a copyright or privacy dispute.
I see there are images on there showing a Coca-Cola can on a table. I imagine that if the Coca-Cola Company saw that on your website, they would sue you to infinity! It’s really not worth poking a sleeping dragon if you can help it…
The concept of Unsplash reads great. But it is a legal minefield. It does expose you to a lot of potential problems - problems you may not have anticipated. I suppose it is not too bad for print media, but for transferable digital media on websites, it’s kind-of the wrong service to be using. It was a shortsighted move for Realmac to include it with RapidWeaver IMO.
As I have said many times before, everyone is capable of taking decent photographs on a smartphone and using creative software to spruce them up a little. Such images are perfect to use on a website. Not forgetting there’s also lots of truly genuine, expert, friendly photographers who are worth chatting with.
They say that “everyone has a novel in themselves”. I like to think that everyone has a photographer inside themselves too! Give it go - try taking and editing a few pictures yourself.
Sometimes you see the same stock images reused time and time again on websites. It really does cheapen a website. Whereas if you use your own images, that solves many of the copyright issues and instantly makes your website more distinctive.