You dont need to use the mail app to paste the photos the way that I'm talking about.
Do you have a word processing app on your iPad? Like Pages perhaps? If you do you could open a new document and tap and hold down on the screen in order to get the Paste option to pop up and paste the photos into that document. I don't know that it would work anyway. I'm just throwing out different ideas.
Or has the mail app completely locked up the iPad and you can't use it all?
Did you try to force quit Mail and then restart?
Force quit the app by holding down on the sleep button until the red slider appears. Let go of the sleep button and then hold down on the home button until the app quits. Restart the iPad. Restart the iPad by holding down on the sleep button until the red slider appears and then slide to shut off. To power up hold the sleep button until the Apple logo appears and let go of the button.