Refer to iPhone email app: it allows users to manage a lot of mails. Its UI pattern may help.
First you tap "Edit" button, then you tap each photo you like to manage, lastly you tap one of the options located at the bottom of a screen.
Googled images:

This UI solves:
- Edit is not a hidden feature (like tap and hold in Safari)
- You wont do changes by accident: buttons are located in a way that user can't do unexpected things accidently doubletapped at the same place
- Clear open / select distinction
2016 UPD
Apple 3D touch is here https://www.youtube.com/watch?v=cSTEB8cdQwo