If you are looking for new themes visit the AppCenter. Once installed you can change using the quick guide below. For a more in-depth guide to themes, see the tutorial on themes.

1.) Selecting the Moksha Theme 

Location: Menu->Settings->Theme

Select the theme from the System list and then hit the apply button.

2.) Select the GTK Application Theme

Location: Menu->Settings->All->Look->Application Theme

Scroll down till you find the matching GTK theme and select it. Then hit the apply button.

3.) Using the Wallpaper

Location: Menu->Settings->Wallpaper

Check the Use Theme Wallpaper box and then hit apply.