Add `640x300.xcf' and `640x480.xcf' files to
    `Modern/2/Backgrounds/Xcf' directory:
    
        - These images are very peculiar because its low resolution needs.
          I needed to make some tunning before exporting them to PNG.
    
        - Regularly, I use the exported `800x600.png' image to create low
          resolution images in different dimensions. However, sometimes
          the resulto of `800x600.png' image isn't good for lowering color
          informacion and also get an acceptable result, so it is needed
          to create an xcf file for each of these images.