I would happily donate a few terabytes, and a fat internet connection.
I don't really understand the niche that Imgur is serving. Past a point, it makes far more sense to have it on your own server (local or cloud), your own CloudFlare account in front of it etc. This weird middleground where people aren't making money off of their content, but still want to share it, but don't actually get that much traffic is a weird one.
Why not just stick some ads on it if you're getting that much traffic or stick it on someone else's ad-supported platform? And if it's porn, why not go through a porn site and monetize legitimately? Surely all legitimate and consensual pornography wouldn't have a problem with that, and they would get more traffic on the ads/subs, and thus more money.
My thought is the only way to fix this is charge users to upload their content, at a rate of ~$2.50/GB. Stick it in the Internet Archive and give them $2/GB (their cost per GB for perpetual storage), and front it with Cloudflare with the other 50 cents (assuming requests for all content eventually trails off theta style). Someone has to not be the object store of last resort, but also the wallet.