Sarah Lane's app cap award on iPad Today 211 went to an app called "Matter" by Pixite LLC. With Matter, you can add 3D effects, shadows, shapes, reflections and more to your photos. You can even animate the effects you create and export it all as a video loop. This is a great way to add an artistic or sci-fi element to otherwise ordinary photos.
There are 4 packs of models available, from simple geometric shapes to more complex structures. You also have control over its visual style, like whether it will be reflective or refractive. Built-in masking tools allow you to erase parts of the model so it will blend in with the photo better. To make it even more realistic, you can add and adjust the shadow cast by the model. If you want to animate your creations, Matter gives you the option to make it spin, pulse, or hover in the picture. Then you can customize the rotation speed and direction to make it more unique.
If you're not so sure about the app, there are plenty of free background images that you can experiment with in Matter's "Free for All" photo browser. These are photos submitted by the community that you can edit and share. When you're done with your creation, Matter will send the photo or video clip to Instagram so you can instantly share it.
To see a demonstration of Matter, check out iPad Today episode 211 with Sarah Lane and Leo Laporte.