Cornell Box on White Background

Skybox is commented. 

            <babylon extends="minimal">
              <!-- Ground that receives shadows -->
              <ground receive-shadows="true"></ground>
              <!-- Default skybox
             <skybox></skybox>
             -->
                     <model url="https://models.babylonjs.com/CornellBox/cornellBox.glb">
                    </model>
              <!-- enable antialiasing -->
              <engine antialiasing="true"></engine>
              <!-- camera configuration -->
              <camera>
                <!-- add camera behaviors -->
                <behaviors>
                  <!-- enable default auto-rotate behavior -->
                  <auto-rotate type="0"></auto-rotate>
                  <!-- enable and configure the framing behavior -->
                  <framing type="2" zoom-on-bounding-info="true" zoom-stops-animation="false"></framing>
                  <!-- enable default bouncing behavior -->
                  <bouncing type="1"></bouncing>
                </behaviors>
              <position x="3" y="3" z="3"></position>
              </camera>
              <scene>
                <clear-color r="1" g="1" b="1"></clear-color>
              </scene>
            </babylon>

You may play with clear-color parameter (here – white color).