Iwould like to see the ability to sketch on an image or photograph.
Consider the scenario of a app used to inspect cars after an accident. It would be very useful to have a series of vehicle outline images (side, front, back, top) that an inspector could access and then mark up. Likewise once a photograph is taken and put in a collection it would be good to be able to annotate it.
In other forms app solutions I have got around this by using other apps on the device, saving an image form these into the local store and then attaching this to the form. This was not ideal as it had issues around audit trails and passing round the base vehicle images. I dont believe Powerapps can access say the local camera roll yet.