Can I keep my old iPhone 4s and still get a newer phone on my plan?

I have an iPhone 4s and while it's not the fastest, it still works fine. However, I'm doing a lot this summer and need more space for pictures (the 6gb my current phone has won't suffice). However, I write a lot on my 4s and would like to simply turn it into an iPod and get a newer phone (5s or higher) and make that my current phone instead. When I talked to someone at a Verizon store, they said I could get a new phone if I traded in my current one, but I would still like to keep it, and get a brand new phone to start off with, a clean slate… Can Verizon just go into my account and deactivate the phone part of my 4s and let me get a new iPhone?

Of course. You do not need to trade in your older one, you can always just a get new one as thats up to you but they would give you some money off if you traded in the old one.

Personally I would just use your new one for everything and sell the 4S as no reason to hold it and let it depreciate as then you won't get any money back out of it (unless you really are going to use it alot instead of the new one as you said but I don't see why).

Pictures are a non issue by the way, just unload them to the computer and remove off the phone, thats what I do. (I delete ones I don't want to keep).