PxKnit is an app that lets you dynamically knit together two pictures. The controls in the app allow you to shape and color various elements, and how rows and columns relate to each other.
Tap and hold on an input item to bring up the context menu to select a source for the input. The left and right input sources can be either a photo that you capture within the app, one from your photo library, or a solid color.
Tap and hold on the output item to bring up the context menu to select the background and border color.