When sending a new message there are two quick options available.
To swiftly send a picture, tap and hold the camera icon. Slide straight up to capture a shot and send it, while sliding right will start a video recording. Let go of the button and it will send it on.
To send an image from the Photos app, tap the camera button quickly. Choose from recent images or select Photo Library to choose an older image.
On the other side of the input box there is a microphone icon. Tap and hold this to record an audio message then slide up to confirm and send it.