We only have a few active restrictions regarding plugins or themes. It is always best to use software that is available on WordPress.org.
There is also no need to install your own backup plugins, as backups are included as part of our services by default.
Be cautious when using software purchased from sites like ThemeForest, particularly with so-called coach, marketing, or sales themes, and/or software that can resize images (such as Timthumb). These are often insecure, and we may request that you remove them.
The plugins we block on certain servers are: adminer, ewww-image-optimizer, wordfence, wp-phpmyadmin, wp-postviews, wp-slimstat.
We do this to ensure better speed and security for every site. Many of these plugins significantly slow down the site, and there are good alternatives available (for example, wp-postviews and wp-slimstat can be replaced by the free Google Analytics).