Using media servers with Prestashop is a great idea to speed up your site, but if you do not have a wildcard SSL certificate you cannot really run them. Sure you can use services such as MaxCDN or similar, but if you are on a tight budget it might not be feasible. Let me show you how you can get all of the benefits of media servers, without having to use an external service or having a wildcard SSL certificate.
The code below works with Prestashop 1.5, all you have to do is create a file named Tools.php in the overrides/classes directory and paste the code below into it. Then you add your media servers like normal. You will have to flush the Prestashop cache to enable the changes.
If the file is already created, it might just be blank depending on the version of Prestashop you are using. If it has content in it, it could have an override already added to the file. If that is the case you will have to hand merge the override.