How add a jpeg file to gazebo

edit

I just had a similar need - a carpet on the floor. What worked for me was the following (with Gazebo 1.9):

1) In the world file:

<model name='carpet'>
  <link name='link'>
    <visual name='visual'>
      <geometry>
        <box>
          <size>12.88 12.88 0.005</size>
        </box>
      </geometry>
      <material>
        <script>
          <uri>file:///full/path/to/materials.material</uri>
          <name>Materials/Carpet</name>
        </script>
      </material>
    </visual>
  </link>
  <static>1</static>
</model>

2) materials.material file:

material Materials/Carpet
{
  technique
  {
    pass
    {
      ambient 1.0 1.0 1.0 1.0
      diffuse 1.0 1.0 1.0 1.0
      specular 0.2 0.2 0.2 1.0 12.5

      texture_unit
      {
        texture carpet14x14.jpg
        filtering trilinear
      }
    }
  }
}

I pulled this one from somewhere else and just replaced the script name and texture filename.

3) carpet14x14.jpg in the same folder as materials.material