Nginx uploadprogress module
For Drupal and maybe for other web applications as well, to use and see the progress of files uploaded normally we need the nginx-upload-progress-module for Nginx.
Many alternative repos for rhel for example are integrating this to support Drupal hosting (and really this is important for us Drupal users/developers).
This is from drupal.org:
https://drupal.org/project/filefield_nginx_progress
That's the module we are using on Nginx with that module.
Other way would be if you would support official/3rd party Nginx builds and control it from Plesk (like Apache, PHP, MySQL is).

Unfortunately, we have to close your request, because over the years it has not become quite popular for further implementation.
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IG
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Madalin Ignisca commented
For our server, we have switched to Debian 7.x as we have analyzed it and it has default packages perfect for our projects.
Still, for Nginx, the package that comes with Plesk has very limited support for some necessities for Drupal hosting.
Drupal is one of the most popular web apps used in the world, and it has some cool features for Nginx for performance and solve some issues that really drive us crazy.
Default Nginx packaged in Debian 7.x has 3rd party modules optional in separate packages. We need some of those, so for Debian 7, the distro's package would be much better.
Plus it is guaranteed more stable then the 1.5 unstable version packaged with Plesk.
At least you shoud give us the option to choose between your version or the distro's version.