I like to play around with themes and icons to make my desktop looking more lovely. Can I use the themes and icons also for Unity 3D/2D, or what do I have to look for to know when and how I have to use them?
What themes you can use with Unity depends on the version of Ubuntu you are running.
- Ubuntu 11.04 or earlier: Use GTK+ 2 themes.
- Ubuntu 11.10 or later: Use GTK+ 3 themes.
If you are running Ubuntu 11.10 or later, you can use the same themes you would use with GNOME 3 (or, more accurately, GNOME Shell). This is because Unity itself is based on GNOME 3 in those versions. Unity in Ubuntu 11.04 and earlier is based on GNOME 2, so it uses a different set of themes.
Icon sets should be completely compatible with any Ubuntu release under any GNOME-based desktop environment (including Unity). Also, there should be no theme differences between Unity 3D and Unity 2D.
You can get themes and icon sets from sites like gnome-look.org or deviantART. After you download your desired theme sets, see How do I change to a theme not listed in the Appearance screen? or How do I get and install more themes, icons, and pointers? for information on how to apply them.
First, install GNOME Tweak Tool from the Ubuntu Software Center.
Once you download a theme or icon set you'll have to extract the theme or icon set and put it in the right folder. Use
gksu nautilus to navigate to the downloaded file then right-click to extract the theme's tar or zip. Then, put that extracted folder in
/usr/share/themes if it's a theme or
/usr/share/icons if it's an icon set. After that, open GNOME Tweak Tool and go from there.