You can add an HDR-style effect to the image, whereby the darker areas appear brighter and the bright areas appear darker - giving your image more dynamic range. This gives you an image which looks more akin to how the human eye sees it, rather than a camera.
Image sharpening tools emphasize the edges within an image. This can be applied to a blurred image to make it appear sharper and more detailed.
You can apply a mirror effect to the image, allowing you to experiment with creating symmetrical images.
Tilt shift is a technique which can be used to achieve the “diorama” effect, whereby you can make normal images look as if they were taken of small models. It works by applying a blur to parts of the image which simulates a shallower depth of field, even on objects far away.
You can add captions and titles to your photos.
When taking a picture with the app, you can preview your next photo with the filter already applied. This means you can choose a filter that compliments the scene before you capture the image, rather than applying it later.