Josh

This plugin will allow you to add a custom welcome message to your login/register screens. It will also allow you to add a separate custom message for your logout screen. The admin page allows you to add HTML code into the message boxes, so you can include images, links, videos, or any other HTML code. The options are only limited by your imagination. Check out the screenshots for an example.
Features:
<ul>
<li>Add a custom welcome message to all users who visit your login/register page.</li>
<li>Add a separate custom message to your logout page.</li>
<li>Change the default wordpress logo to your own custom image.</li>
<li>Change the default hover text from “Powered by WordPress” to your own custom message.</li>
<li>Change the default logo link from “www.wordpress.org” to your own custom link.</li>
<li>Manipulate the CSS for the message boxes to make beautiful effects and custom styles.</li>
<li>Add links, images, videos, embeds, iframes, or any other HTML compliant tags.</li>
</ul>
Support: 
<a href="http://forum.joshlobe.com/member.php?action=register&referrer=1" rel="nofollow ugc">Visit my support forum.</a> 
<a href="http://www.joshlobe.com/2012/01/wordpress-custom-welcome-messages/" rel="nofollow ugc">Visit my personal blog page for this plugin.</a>
Other Plugins by Me: 
<a href="https://wordpress.org/extend/plugins/ultimate-tinymce/" rel="ugc">Ultimate TinyMCE</a> – Finally unlock the true power of your visual editor.
<h3>Features</h3>
<ul>
<li>Add a custom welcome message to all users who visit your login/register page.</li>
<li>Add a separate custom message to your logout page.</li>
<li>Change the default wordpress logo to your own custom image.</li>
<li>Change the default hover text from “Powered by WordPress” to your own custom message.</li>
<li>Change the default logo link from “www.wordpress.org” to your own custom link.</li>
<li>Manipulate the CSS for the message boxes to make beautiful effects and custom styles.</li>
<li>Add links, images, videos, embeds, iframes, or any other HTML compliant tags.</li>
</ul>

Custom Welcome Messages

This plugin will allow you to add a custom welcome message to your login/register screens.  It will also allow you to add a separate custom message fo …

Walid Sadfi

The Conditionnal Maintenance Mode for WordPress plugin allows the administrator to enable or disable maintenance mode for selected user roles. The administrator can also customize the maintenance message that will be displayed to users who do not have the necessary roles.
This plugin is useful when you are performing updates or maintenance on your website and want to limit access to certain users while you work.

Conditionnal Maintenance Mode for WordPress

This plugin allows the administrator to enable or disable maintenance mode for selected user roles and customize the maintenance message.

Custom Welcome Messages vs Conditionnal Maintenance Mode for WordPress