Lots of users have reported different problems with iMessage. If you use this application, you almost certainly experienced those issues yourself, you can find 5 ways to fix iPhone 6 iMessage freezing and crashing problems that will help you to use your favorite app again
This is perfect solution if the application crashes when you tap on the photo icon in iMessage. You should:
1. Go to Settings and choose General
2. Choose Reset
3. Tap on Reset all Settings.
This action will not erase your data. However, one time you are finished, you will need to redo your personal settings.