I suspect you will have a very hard time uploading that much data into less than a series of 20 sites. Our CDN is optimized for much smaller files, and also for much smaller deploys.
However, we charge for transfer, so anyting you can fit in, that is referred to by your html, is not against our ToS. This is in contrast to say uploading something that is used just by e.g. a game that runs on people’s PC’s and pulls art from our servers via API, rather than in a browser.
TL;DR feel free to give it a try but I would be surprised if you could create a 15Gbyte single site.