I don’t know if many of you know it, but there’s a Haiku GNOME theme, complete with cursor and icon packs ready to be installed in Linux. Aside from the absence of the window tabs, my GNOME desktop now looks just like Haiku 
Download:
http://ubuntu-art.org/content/show.php/Haiku?content=106952
Ha! Neat.
Too bad the title bar spans the entire window–that would make it too cool, though.
ZevenOS also provides a GTK- and Icon-Theme which resembles Haiku.
You can get it from here: http://www.zevenos.com/de/download/themes