The idea is nice, but the actual images are completely wrong. WiFi is just electromagnetic waves and those in turn are nothing other then light at another wavelength, i.e. a different color if you will, see this infrared image. This means being able to see WiFi signals would look fundamentally no different then just seeing ordinary light. You wouldn't see waves shooting out of your router, as you can't see waves unless they actually hit your detector, so the thing would simply glow like a light source. The thing where it gets interesting is in how different materials react to the WiFi, materials that are obaque to regular light would be transparent for WiFi signals, while others that are transparent for light would be opaque to WiFi. How much or how little WiFi gets reflected would also change. Being able to see how directional the signal of different antenna could also be interesting. There might also be issues with image resolution, as the wavelength determines how good you can resolve an image (not sure if that's just a practical limit of detector size or actually a physical limit).
Anyway, some simple photoshopping won't cut it, it would probably need a raytracer to simulate the wave propagation properly.