How do I create a custom theme, or layout using images? I would like to create a custom theme, for which I have the images for parts of the theme, such as header, footer, menu, logo. I don't understand how to start to create a layout. I have gone through "Themeing guide," but I don't know where to start.
You should download a theme such as AdaptiveTheme  or Zen as a base and then create a sub-theme.