With HTML, you can suggest a background image with the BACKGROUND attribute of the BODY element. Here is an example:
<body background="imagefile.gif" bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080" alink="#000080">
If you specify a background image, you should also specify text, link, and background colors since the reader's default colors may not provide adequate contrast against your background image. The background color may be used by those not using your background image. Authors should not rely on the specified background image since browsers allow their users to disable image loading or to override document-specified backgrounds.