We've seen a few apps that add Hollywood-type FX to your videos, but here's an app that does the same for your photos.
LensFX (free with some in-app purchase options) will let you take a photo, or load one from your camera roll. You can then choose from more than 130 effects to add, like explosions, aircraft, fire and dinosaurs. Each effect can be placed in an individual layer so they can be moved, resized or rotated independently.
There are color adjustments, gradients and vignette settings. There isn't any help, but the app is pretty obvious to use. There is even a cityscape to get you started.
I tried the app with some of my landscape photos, adding a rampaging reptile and an attack helicopter. I also placed some missiles with a smoke trail over some familiar landmarks. The effects are of very high quality, and the dinosaurs cast a realistic shadow. You re-size by pinching or expanding two fingers on your screen, and there are options to flip the image.
There is a nice collection of lens flares which look good too, and various explosions so you can blow up anything with style.
In-app purchases are US$0.99 and include robots, more fire FX, a greater variety of dinosaurs, jets and helicopters.
If you want to really go extravagant on FX, you might want some of the extras, but I found the basic free app had enough to make some striking and colorful photos.
I found placement of the objects sometimes tricky. An errant tap would take the effect right off the screen, and I had to re-apply it. Still, the app was mostly predictable and I did not see any crashes (other than planes and missiles).
The same developers gave us Alien Sky, which is another high-quality app for augmenting photos.
LensFX is a universal app, and requires iOS 6 or later. It is optimized for the iPhone 5. It's definitely worth a download if you love to modify your photos.