Install a screen, part 1
A truly futuristic robot, of course, has an interactive display. Look no further than your smartphone, tablet, or iPod Touch, any of which can be repurposed for costume duty. Cut a screen-size hole in the body, and mount the device behind it, or build a frame for the device that attaches to the outside of the body, thus giving it some extra dimension. Either way, make sure that only the screen is visible, otherwise it ruins the effect. And be sure to adjust the settings so the screen never dims or shuts off while you're wearing the costume.