My attempt at making a tango theme for XFE. I used http://xfce-look.org/content/show.php/MY_XFE_ICONS?content=49889&PHPSESSID=c69d699959eaaf56f3c0b2e28574587b as a template. I kept the makefiles intact, so it should work on versions below 0.88 , although I made it in version 0.99.
Lots of the mime types (the icons for specific files, ie; a musical note for an mp3, a cabinet for .zip ,etc) are still pretty dull and don't go too well with the theme, as I only modified the worst ones. If you want to change/add some icons, you can get some good ones here: http://tango.freedesktop.org/Tango_Icon_Gallery
This theme doesn't look that great in big icon mode, as most of the images are 16x16 pixels. I suggest that you use small icon mode or list mode.
Extract the zip file to /usr/share/xfe/icons/hashed-tango-theme/ , run XFE, goto Edit > Preferences , click on the Themes tab and change the icon path to /usr/share/xfe/icons/hashed-tango-theme/ . When you click accept you should be told to restart XFE. Do as it says and the next time the program runs the new icons will be used.