GREAT !!
Back up PC photos to old cell-phone.
Just what I was looking for. 
All cellphones manufactured for North America MUST dial 911 even if the phone is old or unused!!!
If the phone can still be charged up it can be used as an emergency phone, forever. All carriers MUST send the 911 call through even if you’re not a customer. Think twice about tossing it out, keep it in the glove box for accidents reporting.
I was going to mention the 911 thing, but I believe the ability to call 911 used to be that only after it sucessfully was used with a carrier first. Now it appears that an unregistered phone can also call 911 before it is ever registered to a carrier initially. Know that without an active carrier, 911 will not see your location or be able to call you back.
There are free phone numbers you can get and use them with wifi on the phone to make and receive calls, but not dial 911 directly.
You can use an old cell phone to play games, make wifi calls, use it to take photos and transfer them to a computer through a hardwire connection or through wifi or near field connection (wifi bluetooth). You can use bluetooth to remotely play music or see videos. You can link the cell phone to certain versions of Windows or your TV, etc. You can use the video capability to stream to another system in the hous (remote camera) or maybe use it with Zoom and so on.
On some cell phones (my Android for example) there are apps to see GPS location and I can access all sorts of internal sensors (temperature, GPS, use as a metal detector, proximity, speed of movement, etc).
Some cell phones may allow you to use them to charge another cell phone or device, as if it were a power bank. I recently aw how you might be able to use near-field to charge another device.
Even turned off, I can use it to ward off panhandlers and petition signature hopefulls who think I am actually talking to someone on the phone when I am not.
Also, I can use an old cell phone as a paperweight to kep paper from blowing away in a breeze.