I want to create a simple office-like environment from an image. One possibility would be to create it using heightmaps, but I was not able to do so with only a single texture or plain color (the examples I could find all use three textures...).

Another more obvious option, since I only have 1 height, is to use the "image" option. However I have not been successful with my various tries. I am using ros fuerte with the gazebo that comes with it.

You can find below the latest environment I tested:

<gazebo version='1.0'>
  <world name='default'>
    <scene>
      <ambient rgba='0.1 0.1 0.1 1.0'/>
      <background rgba='0.7 0.7 0.7 1.0'>
        <sky material='Gazebo/CloudySky'/>
      </background>
      <shadows enabled='1'/>
    </scene>
    <physics type='ode' update_rate='0.0'>
      <gravity xyz='0.0 0.0 -9.8'/>
      <ode>
        <solver type='quick' dt='0.001000' iters='50' precon_iters='0' sor='1.3'/>
        <constraints cfm='0.0' erp='0.1' contact_max_correcting_vel='100.0' contact_surface_layer='0.001000'/>
      </ode>
    </physics>

    <!-- Ground Plane -->
    <model name='plane1_model' static='1'>
      <link name='body'>
        <collision name='geom_1'>
          <geometry>
            <plane normal='0 0 1'/>
          </geometry>
          <surface>
            <friction>
              <ode mu='10.0' mu2='10.0' fdir1='0 0 0' slip1='0' slip2='0'/>
            </friction>
            <bounce restitution_coefficient='0' threshold='1000000.0'/>
            <contact>
              <ode soft_cfm='0' soft_erp='0.2' kp='1e10' kd='1' max_vel='100.0' min_depth='0.0001'/>
            </contact>
          </surface>
        </collision>

        <visual name='visual_1' cast_shadows='0'>
          <geometry>
            <plane normal='0 0 1'/>
          </geometry>
          <material script='Gazebo/White'>
            <emissive rgba='1.0 1.0 1.0 1.0'/>
          </material>
        </visual>
      </link>
    </model>

    <model name='map' static='1'>
      <link name='link' gravity='1' self_collide='0' kinematic='0'>
        <origin pose='0.0 0.0 0.0 0.0 -0.0 0.0'/>
        <collision name='collision' laser_retro='0.0'>
          <geometry>
             <image filename='willowMap.png' scale='100' threshold ='200' height='1.0' granularity='1'/>
          </geometry>
        </collision>
        <visual name='visual' cast_shadows='1' laser_retro='0.0' transparency='0.0'>
          <material />
          <geometry>
             <image filename='willowMap.png' scale='100' threshold ='200' height='1.0' granularity='1'/>
          </geometry>
        </visual>
        <damping/>
      </link>
    </model>
    <model name='table1' static='1'>
      <origin pose='2.0 3.0 -0.010 0.0 0.0 -1.570800'/>
      <link name='body' gravity='1' self_collide='0' kinematic='0'>
        <origin pose='0.0 0.0 0.0 0.0 -0.0 0.0'/>
        <collision name='top' laser_retro='0.0'>
          <origin pose='0.0 0.0 0.620 0.0 -0.0 0.0'/>
          <geometry>
            <box size='1.4 0.5 0.050000'/>
          </geometry>
          <surface>
            <friction>
              <ode mu='-1.0' mu2='-1.0' fdir1='0.0 0.0 0.0' slip1='0.0' slip2='0.0'/>
            </friction>
            <bounce restitution_coefficient='0.0' threshold='100000.0'/>
            <contact>
              <ode soft_cfm='0.0' soft_erp='0.2' kp='1000000000000.0' kd='1.0' max_vel='100.0' min_depth='0.001000'/>
            </contact>
          </surface>
        </collision>
        <visual name='top_visual' cast_shadows='1' laser_retro='0.0' transparency='0.0'>
          <origin pose='0.0 0.0 0.010 0.0 -0.0 0.0'/>
          <geometry>
            <mesh filename='table.dae' scale='1.0 1.0 1.0'/>
          </geometry>
        </visual>
        <damping/>
      </link>
    </model>

    <light name='directional' type='directional' cast_shadows='0'>
      <origin pose='0.0 0.0 100.0 0.0 -0.0 0.0'/>
      <diffuse rgba='1.0 1.0 1.0 1.0'/>
      <specular rgba='0.10 0.10 0.10 1.0'/>
      <attenuation range='200.0' linear='0.010000' constant='0.500000' quadratic='0.001000'/>
      <direction xyz='0.010 0.0 -0.990000'/>
    </light>
  </world>
</gazebo>