**Images (of movie clips) used as background in the 3D viewport are primarily meant to be used as reference and will not render**.


Here are a couple of alternatives:

 - **Using the compositor**

  Add an Input>Movie Clip node, and use an alpha over node to compose the render layers over it.

 [![enter image description here][1]][1]


 For single images use an Input>Image node.

 [![enter image description here][2]][2]

 If you are using cycles make sure that you enable **Film Transparent**, so that the rendered layers render with a transparent background:

ver 2.8X and newer

[![enter image description here][3]][3] 

(for ver 2.79 and earlier)

[![enter image description here][4]][4]

 - **Without the compositor**

 Without using additional geometry or compositing, you can use the image as background for the world. Set the Texture coordinates to Window.

 [![enter image description here][5]][5]


 In this case disable Film>Transparent


  [1]: https://i.sstatic.net/oEUTc.png
  [2]: https://i.sstatic.net/egSQs.png
  [3]: https://i.sstatic.net/YRbpP.png
  [4]: https://i.sstatic.net/MOnlM.png
  [5]: https://i.sstatic.net/blzHI.png