Download the "default.dll" from desired Theme in the ChromeSpot Themes Forum and replace Chrome's existing default.dll located here:
Code:
C:\Documents and Settings\username\Local Settings\Application Data\Google\Chrome\Application\version number\Themes
This folder is hidden other normal circumstances, so make sure you select "Show Hidden Files and Folders" in Folder Options if it doesn't display at first.
Make sure you backup your original default.dll so you can restore it later if you would like. You can simply rename it default-old.dll for convience sake.
[Thanks to nathan42100, the original author!]