Tools > AVD Manager, select the “pencil” to get to “Virtual Device Configuration”.
Show Advanced Settings > Camera will give you the option of using emulated, or a device:
Device – use host computer webcam or built-in camera
If all you need is to get a still image into the camera, starting with Android Studio 3.2 you can put your static images into the virtual scene:
as discussed in this entry from Android developers blog. Note that you’ll need to move the camera position into the dining room to see your images (turn around and use Alt-w to move forward).