theme
The option documentation is properly formatted yet
Default: Example: name_of_theme_folder Since: 1.3.8
Use this option to use a specific theme. The theme folder can be located either in share/fs-uae (a bundled theme), or in (My) Documents/FS-UAE/Themes.
Source: https://github.com/FrodeSolheim/fs-uae/blob/master/docs/options/theme