Range: floating point number (frames)
The default number of frames, in the mash's rate, that the theme is visible.
backcolor: six character hex color value
editable: comma delimited list of property names
forecolor: six character hex color value
id: single word string identifier, starting with a letter
map: rain, ripple, fisheye
length: floating point number (frames)
symbol: a valid SWF URL, followed by an ampersand and class name
type: the string 'theme'