mdoff

It’s not a standalone plugin requires installed Contact Form 7
This plugin solves problem of e.g. email verification or email confirmation.
Just create second field with <code>_confirm</code> at the end of the field name. Look in the screenshots for example.

cf7 Confirm Field

Plugin allows to make sure that e.g. emails in two fields are the same

Freemius

TinyGiantStudios

<h4>Contact Form 7 Designer</h4>
Making your contact forms look nice should be easy. Finally it is!
Contact Form 7 Designer lets you design a highly customisable contact form which you can display wherever you want it using a shortcode. All designs are easy to create with a comprehensive backend editor. The best thing is: You don’t need any coding skills whatsoever.
Contact Form 7 Designer, at a glance..
<ul>
<li>Simple. All you need is WordPress and the base Contact Form 7 plugin.</li>
<li>Beautiful. Your form designs are limited only by your creativity.</li>
<li>Customizable. With the Pro version, you can customize even more fields.</li>
<li>Integrates with Contact Form 7 and all the other add-ons.</li>
<li>Developer friendly.</li>
</ul>
<blockquote>
<h4>Contact Form 7 Designer Pro</h4>
This plugin has a premium version which comes with the following features.
Ability to add designs for ALL fields 
 No advertising or premium upgrade notices 
 Easy import / export functionality to transfer designs 
 Use across multiple websites without extra licenses 
 Access to sample forms that you can import 
 WordPress customizer integration for real-time design (coming soon) 
 Priority Support
<a href="http://tinygiantstudios.co.uk/product/contact-form-7-designer-pro/#utm_source=wp-plugin-repo&utm_medium=link&utm_campaign=after-features-link" rel="nofollow ugc">Upgrade to Contact Form 7 Designer Pro</a>
</blockquote>
Add-on plugins
There are several add-on plugins available for Contact Form 7, which help you get even more out of your site.
<ul>
<li><a href="https://wordpress.org/plugins/contact-form-7-gravity-forms/" rel="ugc">Gravity Form Importer for Contact Form 7</a> – Imports forms from the Gravity Forms plugin.</li>
<li><a href="https://wordpress.org/plugins/contact-form-7-honeypot/" rel="ugc">Contact Form 7 Honeypot</a> – Adds enhanced anti-spam features to your contact form.</li>
</ul>
Bug Reports
Bug reports for <a href="https://github.com/TinyGiantStudios/cf7-styles" rel="nofollow ugc">Contact Form 7 Designer are welcomed on GitHub</a>. Please note that GitHub is not a support forum.
More information
<ul>
<li><a href="http://tinygiantstudios.co.uk/product/contact-form-7-designer-pro/" rel="nofollow ugc">Contact Form 7 Designer Pro</a>, containing <a href="http://tinygiantstudios.co.uk/product/contact-form-7-designer-pro/" rel="nofollow ugc">additional features</a>.</li>
<li>Developers: fFllow or contribute to the <a href="https://github.com/TinyGiantStudios/cf7-styles" rel="nofollow ugc">Contact Form 7 Designer on GitHub</a></li>
<li>Other <a href="http://tinygiantstudios.co.uk/#utm_source=wp-plugin-repo&utm_medium=link&utm_campaign=more-info-link" rel="nofollow ugc">WordPress plugins</a> by <a href="http://tinygiantstudios.co.za/" rel="nofollow ugc">Tiny Giant Studios</a></li>
<li><a href="https://twitter.com/tinygiantstudio" rel="nofollow ugc">@tinygiantstudio</a> on Twitter</li>
</ul>
<h4>Bug Reports</h4>
Bug reports for <a href="https://github.com/TinyGiantStudios/cf7-styles" rel="nofollow ugc">Contact Form 7 Designer are welcomed on GitHub</a>. Please note that GitHub is not a support forum.

Contact Form 7 Designer

Contact Form 7 Designer allows users to design their form to fit in with the look & feel of their website.

cf7 Confirm Field vs Contact Form 7 Designer