The easiest way i could come up with not using ssh winscp or some linux distro is by xterm.
Just type this in@xterm:
sudo gainroot 'enter'
cp -r /usr/share/themes/yourthemetocopy /home/user/MyDocs 'enter'

Then just plug in you phone to the pc and transfer theme folder

I just did and it worked

(to do this you need rootsh installed)