Here are reviews of some of the most popular toy camera apps for Android.
By "toy camera app," I mean an app that includes its own image-capture capabilities, rather than using another app such as Android Camera, but which delivers reduced resolution (usually 1 megapixel or less) or which forces the use of filters. In other words, there's no way to take a straight full-resolution picture with a toy camera app. Obviously, these apps are for having fun with, not for anything like serious photography.
The smart-phone that I used for testing these apps produces 2560x1920 (5 megapixel) images. It's possible that some of the resolution figures will be different on other devices.