I've never done adult hosting. But, glancing at those plans, the difference between Webair and vpslink, which I've used in the past, seems to be you get more bandwidth but less disk space at vpslink. The lowest end vpslink plan gives you 2.5GB of storage, no idea if that's enough for your pictures.
But, webair called itself virtual hosting, but that sounded like a stretch to me. It sounds like shared hosting, but you get your own apache instance. However, all the apache instances for all the users running on the same OS install, I think. Someone who's used it would know more.
VPS Link didn't seem that much more expensive for what I looked at. And, it uses real virtualization with Xen. Which means there's actual hardware support for sharing time between all the users. It's not just the less stringent operating system's ability to share processing between the users.
My experience in the past with shared hosting has been dismal. But, maybe webair does a better job?