If you are attracted to brown themes, you can really enjoy this wood theme that is available for Gnome desktops. In this tutorial, we will help you install it under Ubuntu 12.04/11.10. Here is a screenshot of this wood theme under Ubuntu 12.04:
Start the terminal and run these commands:
sudo add-apt-repository ppa:upubuntu-com/themes
sudo apt-get update
sudo apt-get install wood-theme
To enable it, run these commands:
gsettings set org.gnome.desktop.interface gtk-theme 'wood-theme'
gconftool-2 --set --type string /apps/metacity/general/theme 'wood-theme'
Credits for this theme go here.