1. An image processing system, comprising: plural image pickup devices, each including an image pickup part configured to capture an original image and a viewpoint conversion part configured to perform viewpoint conversion for the original image to generate a converted image; an image processor operable to synthesize converted images output from the plural image pickup devices to generate a synthesized image; and a display device controllable to selectively displaying the synthesized image and at least one original image output from the plural image pickup devices.