Sajjad Hossain

This plugin allows you to restrict your site users from uploading files of certain types and control the maximum file upload size. Administrator can select the file types and file upload limit by user role. This plugin restricts users from uploading unwanted files using the WordPress media uploader.
It is very simple to use. You will be able give permissions role wise. To restore WordPress’s default selection, just deactivate the plugin.
Any issue? Please let me know (http://sajjadhossain.com/contact-me/).

WP Upload Restriction

This plugin allows you to control upload of files based on file types and sizes.

Moe Loubani

A simple plugin that you can use that will let your clients contact you from right on their dashboard. The email you get 
from them will include a bunch of diagnostic info that you can use to help get an idea about the problem.
This includes:
<ul>
<li>PHP Version</li>
<li>Server type (Apache / Ngnix)</li>
<li>MySQL version</li>
<li>WordPress version</li>
<li>Site URL</li>
<li>Active plugins</li>
<li>Inactive plugins</li>
<li>And more!</li>
</ul>
If you have any questions feel free to visit my website http://www.moeloubani.com and ask.
Enjoy!

WP Dash Support

A plugin that adds a contact form on the dashboard for developers to use to give clients an easier way to contact them.

WP Upload Restriction vs WP Dash Support