The Nexus 7 allows you to attach a single picture and screenshot or grabbed image to an email. With the stock Gmail and Email app, you are able to only attach one at a time, without multiple pictures or other files at once.
How to attach a picture to Email on Nexus 7
* Open the Email app and touch the Compose icon. Set the send address and match addresses from your contacts.
* Touch Menu > Attach file, and select a photo.
* Type the subject and text message. Then touch the Send icon.