do no have the “window-close” icon, if I was a designer I would create that by myself.
I’m looking at many icon themes in these days and none is complete, all inherit from gnome default (which is released under gpl thus it’s not usable in many cases).
I think that there’s too much mess in the floss artwork between incomplete works and incompatibilities between licenses.
UPDATE: Jakub Szypulka created the icon window-close icon, I hope his artwork will be uploaded to the official tango icons theme (otherwise none would be able to find it and licensing would be a mess). I want to thank him here also if we found that CC and GPL are not compatible thus we cannot bundle tango icons within P4A :-(