Best way to have different header images each page on Bouquet theme

I’m currently customizing the Bouquet theme for someone, and they’ve asked me to use different banner images for some of the different pages. I’ve looked through some of the other forum posts on this subject, but none seem to fit how the Bouquet theme was put together.

I don’t have much experience with PHP, but I’ve narrowed down code in question to the header.php file and the “branding” ID in the stylesheet. Here is the code in the header file:

<header id="branding" role="banner" class="clearfix">
		<a class="header-link" href="<?php echo home_url( '/' ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home"></a>
		<hgroup>
			<h1 id="site-title"><a href="<?php echo home_url( '/' ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home"><?php bloginfo( 'name' ); ?></a></h1>
			<h2 id="site-description"><?php bloginfo( 'description' ); ?></h2>
		</hgroup>
	</header><!-- #branding -->

The branding ID in the stylesheet goes like this:

#branding {
	background-image: url(mtwashingtonheader.png);
}

Can someone tell me the best way to modify this code to achieve my goal? Thanks in advance!

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