a theme for sound-monitor_applet contains the following:

* the theme is contained within a directory.
* the layout and filenames for images are specified in a file
  named themedata (see the example included in the source)
* Only the Background image is required, all other items are
  optional. (but a background by itself is just a picture :)
* a themedata file contains 1 or more sections. [Horizontal] is
  required, [Vertical] is used if the theme supports orientation.
  Both sections support all the flags below. To specify a setup for
  the other panel size, append "_Tiny", "_Small", "_Large", or
  "_Huge" when specifying the respective section. For example
  [Horizontal_Small] would be the heading for Small panel size when
  horizontal.
* Any Image can contain an alpha (transparency) channel, multiple level
  alpha is supported (ala PNG, the recommended image format)

Internationalization:
  Item_* types support internationalization by adding another tag
  to the themedata file and supplying a suitable image.
  Example:
    To internationalize the status item for 'es' do this:

    keep the default line:     Item_Status=stat.png 2 20
    and add a translated line: Item_Status[es]=stat_es.png
        (do not add coordinates to the translated lines)

  Note: the translated image should be the same size as the default,
        and in the case of Item_Misc_* must contain the same number
        of animation frames.

Item_Status=filename x y
  filename: name of the image file for mail, this file contains
            4 images vertically, from top to bottom, indicators for
            error, standby, autostandby, and ready.
  x, y: coordinates to place the image within the window

Item_Meter_Left/Item_Meter_Right=filename sections x y horizontal
  filename: Name of the image file for the vu meters, if vertical, this
            file contains 3 images vertically. The images are each a full
            representation of the meter, from top to bottom these are
            blank (no sound), lit (sound is at this level), peak lights
            (the image to represent the peak position). If horizontal is true,
            then the image is 3 images from left to right, instead of top to
            bottom.
  sections: total number of sections within the meter. (number of increments)
  x, y: coordinates to place the image within the window
  horizontal: If true, designated the meter as a horizontal meter, otherwise
              vertical.

Item_Misc_Left/Item_Misc_Right=filename sections x y
  filename: Name of image file for representing the percentage of volume,
            contains image from top to bottom, the top representing 0 Volume
            and the bottom representing 100% Volume.
  sections: Number of image frames within the image file.
  x, y: coordinates to place the image within the window

Scope=filename sections x y vertical
  filename: Name of image file for representing the scope, contains two images
            vertically. The top image represents the scope's background and the
            bottom image represents scope' data colors.
  x, y: coordinates to place the scope within the window
  vertical: When TRUE, the scope data is displayed from top to bottom.