Monetization of slide-hosting service

For about a year now there has been a slideboom project - a competitor to slideshare . The service offers the ability to convert PowerPoint presentations to flash format and store them.
The main advantage over competitors is the high quality of the resulting files, support for animations, audio and video.
The user can upload up to 100 presentations up to 100 MB each. No further special restrictions are imposed.

Now the task is to monetize the project.
For this, it was decided to use paid accounts with additional functionality.
In add. functionality included

• Customizable page without extraneous elements (popular, best presentations, etc.)
• An opportunity to show the presentation to a certain circle of people
• Custom players
• Ability to download converted presentation in swf or exe format
• Increase the number of stored presentations from 100 to 500

The cost of such an account is $ 99 per year.

I don’t want to show ads on the site.

1. What functionality could users of the service pay for?
2. What other methods of monetization of slide-hosting service can be?