In this article we will be seeing how to get all the available SharePoint site
themes using SharePoint object model.
Go to Site Actions => Site Settings => Look and Feel => Site theme.
Programmatically get all the available site themes:
ThmxTheme class:
Represents a Microsoft Office XML theme file. The methods and properties of this
class enable read and write operations on the theme name, the color list, and
the font list. For more information refer
http://msdn.microsoft.com/en-us/library/ee658367.aspx.
ReadOnlyCollection:
Provides the base class for a generic read-only collection.