Monetization slide-hosting service

For about a year, there has been a slideboom project, a slideshare competitor. The service offers opportunities for converting PowerPoint presentations to flash format and storing them.
The main competitive advantage is the high quality of the files, support for animations, audio and video.
The user can download up to 100 presentations of up to 100 MB each. No more special restrictions are imposed.

The challenge now is to monetize the project.
For this, it was decided to use paid accounts with additional functionality.
In add. functional included

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

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

I don't want to show ads on the site.
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1. For what functionality the service users could pay money?
2. What other ways to monetize the slide-hosting service can be?