The size of the things you can see depends on the wavelength of the light.
FM Radio (100MHz) has 3m wavelength. You'll need a giant camera and will be able to see only very big structures.
Wifi/Microwave/Radar is in the Gigahertz range. 2.5GHz == 12cm wavelength. For radar photos, you'll need a very big camera, and a human would be only a few pixels big.
Some airport scanners are based on millimeter waves (teraherz radiation), and you can find sample photos online. They produce pretty blurry pictures, but clothes become partially transparent.
WiFi is closer. High microwave is probably what you want here.
And of course, this already exists. It's called radar. Haven't seen any radar "photos" though. Interesting if that's indeed possible.