With the latest release of Nintex Mobile Apps (April 2015), you can now edit any images you attach to a form. You're able to do this on Android, iOS and Windows Phone.
I took a picture with my device within the Mobile App, and then clicked on the image (See here on How to attach pictures or videos to a form in the Nintex Mobile App).
Here's my kangaroo, but he has a droopy ear which needs fixing.
Click on Edit in the top right hand corner.This will open the Photo Editor where you have options to add text, draw, orientation, crop, blur, and adjust lighting, color and sharpness.
I added a little greeting from this guy using the Text option, but since want I really want to do is highlight his slightly droopy ear, I can use the Draw feature to do that. All I need to do is select the paint color and thickness. Once I'm done, select Apply, and then Done.
The annotated image now appears in the attachments section of the form. Once you've completed the form, you can submit it.