The Omni light component, found in the Lights Extension, can be of great help in scenes that are just a little too dark. It an orb of light that casts light in all directions but isn’t visible in renderings. Place it anywhere in your drawing that appears dark in a rendering.
After placing an omni light in your drawing, you can change the elevation and scale in the green properties box. You can also change the elevation directly in the 3D drawing view with the yellow stretch node. After placement, you can double-click the omni light to open the Light Settings dialog where you can change properties such as brightness, shadows and temperature.
Below are two office renderings; the left image is without the omni light while the right image is with the omni light: