ThemeShock

Custom 404, helps you customize your 404. 
From the dashboard options you’re able to modify the background, the image and the fonts color and style.
This page will show users the last post on your site, so that they may choose to follow one of this instead of leaving your page.
<h3>Features</h3>
<ul>
<li>Customizable background</li>
<li>Several Patterns</li>
<li>Multiple fonts</li>
<li>24 additional images.</li>
<li>5 Different languages</li>
</ul>

Custom 404 Error Page: Unilimited designs and colors

Custom 404, creates a 404 page that is set to the default one of your WordPress installation.
This page is fully customizable from the dashboard.

Samir Shah

This plugin will issue a HTTP <code>410</code> response to requests for articles that no longer exist on your blog. When you delete a post or page, it records the URL for that page and issues a <code>410</code> response when that URL is requested. You can also manually manage the list of obsolete URLs.
The <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.11" rel="nofollow ugc">HTTP Specification</a> defines the <code>410</code> response header for use when a resource has been permanently removed. It informs robots visiting your site that the requested content has gone, and that they should stop trying to access it.
If you come across any bugs or have suggestions, please use the plugin support forum. I can’t fix it if I don’t know it’s broken! Please check the <a href="https://wordpress.org/extend/plugins/wp-410/faq/" rel="ugc">FAQ</a> for common issues.

410 for WordPress

A plugin that sends HTTP 410 (Gone) responses to requests for articles that no longer exist on your blog.

Custom 404 Error Page: Unilimited designs and colors vs 410 for WordPress