There's a lot that could be done to improve the project as it stands now. Why don't you try a few?
Add sharing capabilities to the app. Be careful to deal with batch sharing multiple images, too.
Add filters to the images so that they can be converted to black and white, sepia, and more. If you want to save the files, you'll need to write a native plugin to save the data returned from the canvas.
Speed things up a bit by generating a thumbnail from each image if it doesn't already have one. You could store the thumbnail in local storage if you wanted, it wouldn't be very big, or use the File API to store it.