Window decorations in fvwm-themes are defined within 3 components: colors (defines all theme colors), windowlook (defines border type, title font and allightment) and buttons (defines window buttons). So a user has a lot of flexibility to mix different window decoration aspects.
It is also possible to define only decoration specific colors in component colors-decor, which overrides the corresponding definitions (colorsets 1 to 4 and title background) from colors. And finally, a user may change a title font using font filters from fonts component.
Here are some examples of window decorations possible with fvwm-themes.