The Lutron Aurora smart bulb dimmer is the best solution I've found to cover up an existing switch. Covers it very nicely, is extremely easy to install, is pretty easily removable, and
AURORA 1-10V Rotary Dimmer Switch 1 Gang 2 Way 1-10V DC Input - LEDVista Lighting
Lutron's new dimmer for Hue lights fixes the wall switch problem - The Verge