Implementing sky texture?

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I've been working on getting a skybox for my simulation environment. I noticed that the <sky> SDF tag does not support <material> which means I can't simply import an image onto the simulation environment's sky box. I ended up surrounding the plane with 4 other planes with the appropriate sky texture, but that solution seems to drastically reduce framerate of the simulation environment. Is there a way to import images into the Gazebo sky box? Thanks.