Bhooshan,
A "workaround" generally refers to a way to fix something that shouldn't
be broken, but is. There's nothing broken here.

What you're after can
be accomplished on the client side (handled by the browser) or on the server
side. If you go with client side, you could write a function in JavaScript
that picks an image from a pre-determined array. If you go with server
side, you could do the same thing, but with PHP, ASP, ColdFusion, or the
like.
You could probably Google the terms "JavaScript random background" and
find a good handful of free scripts or tutorials. Even better, you could
take a stab and learning JavaScript yourself ... even the basics can help
you tremendously in regard to dynamic website features.
http://www.w3schools.com/js/default.asp
David
stiller ( at ) quip ( dot ) net