Xfwm4 uses a simple yet flexible pixmap based theme engine using images in .xpm format. It also uses a text file for other configuration options (see themerc section). You can also make a theme pick up gtk theme colours.
editing /usr/share/icons/default/index.theme solved things change from: [Icon Theme] Inherits=core to: [Icon Theme] Inherits=ComixCursors-Blue-Regular (which was the folder name of theme i was trying to get working) then restart X