SkinStudio lets you create your own Start bar, Start button, title bar buttons, push buttons, scrollbars, toolbar icons, progress bars, and much more. It is a free, but ad-supported skin editing application that's advanced.
Here are some screenshots to illustrate the features and user interface of this application:
AutoHotkey
LightBulb
AutoHideDesktopIcons
DesktopOK
Earthview