In the built-in iOS email app - Mail - attaching images to messages is simple—hold a finger down in the message and when you get the pop-up menu, select Insert Photo or Video. In iOS 9, you don't even have the five-image limit anymore.
Better yet, it now includes the ability to annotate or mark up images. With the image inserted, hold your finger on top of it until the pop-up menu appears, then select Markup. Draw on the image with a number of colors, turn the drawings into recognized shapes, zoom in, add some text, or even throw in your signature.