In general, the “cache everything” page rule allows caching any file. But wherever you’re linking your binary files from must also be on Cloudflare and must also be HTML/a website. The terms of service apply to all plans (except maybe when you have an enterprise contract).
For example, Mediafire uses Cloudflare, and can because their main website is also using the Cloudflare proxy.
Can you point me to the location in their TOS that states that the content must be served from a website?
EDIT: never mind, I found it (2.8 Limitation on Non-HTML Caching)
Digital Ocean’s Spaces comes with CDN and may be an affordable option. Keep in mind that their CDN “double charges” outbound data if it has to pull from non-cached data from the bucket and then routes it though the CDN. If it’s already cached in the CDN, it’s a single charge.