I have a problem showing the ground or floor in gazebo.
The part of the world file looks like this:

<rendering:ogre>
<ambient>1.0 1.0 1.0 1.0</ambient>
<sky>
  <material name="sky">
   <color rgba="0.0 0.0 0.0 1.0"/>
  </material>
</sky>
<grid>false</grid>
<maxUpdateRate>10</maxUpdateRate>
</rendering:ogre>

<model:physical name="gplane">
<xyz>0 0 0</xyz>
<rpy>0 0 0</rpy>
<static>true</static>

<body:plane name="plane">
  <geom:plane name="plane">
    <laserRetro>2000.0</laserRetro>
    <kp>1000000.0</kp>
    <kd>1.0</kd>
    <normal>0 0 1</normal>
    <size>51.3 51.3</size>
    <!-- map3.png -->
    <material name="floor">
        <color rgba="0.0 0.8 0.0 1.0"/>
    </material>
  </geom:plane>
</body:plane>
</model:physical>

Tried it with different materials but no change. Same with sky, wanted to change it to a color but also doesn't work.