What do you use to sync contacts? An email account, or iCloud?
Do you use PhotoStream, Photo Sharing, or iCloud Photo Library?
What you could try:
Make sure Contacts is enabled on both devices. Also look at your settings in Settings - Photos, enable the option you prefer, and do this on both iDevices.
Are you connected to Wi-Fi? Try opening a random website.
Also try force closing both apps (Contacts, Photos), maybe they'll start syncing again afterwards.
In the Contacts app, it's possible to "force" the app to sync. When you open it, you'll see "All Contacts" at the top left, and "Groups" next to it. Tap Groups. Then drag down the list of accounts that sync to the app. You'll see a small spinning wheel at the top:
Hopefully this will help syncing contacts.