Justin Tadlock

<p>A plugin for allowing users to set a custom background on a per-post basis.  This plugin hooks into the WordPress <code>custom-background</code> theme feature and overwrites the values on single post views if the post has been given a custom background.</p>
<h3>Features</h3>
<p>This plugin creates a custom meta box on the edit post screen.  From that point, you can select a custom color and/or image.  If you select an image, you’ll be presented with additional options for how the image appears on the site.</p>
<h3>Requirements</h3>
<p>Your theme must support the core WordPress implementation of the <a href="https://codex.wordpress.org/Custom_Backgrounds" rel="nofollow ugc">Custom Backgrounds</a> theme feature.</p>


Custom Background Extended

Allows users to create a custom background on a per-post basis.

Pat Hawks

dirtysuds

<p>Once activated, Gallery posts will have an excerpt that is a row of thumbnail images from that post, rather than some (often not descriptive) text.<br />
This excerpt should appear in your archive pages, and perhaps elsewhere, depending on your theme.</p>
<p><strong>Note:</strong> The post <em>must</em> actually have the post type ‘Gallery’. It cannot just be a post with a gallery in it.</p>


Gallery Excerpt

Replace the excerpt for posts with the post type 'Gallery' to a row of images from the post.

Custom Background Extended vs Gallery Excerpt