1. Lease a dedicated server 2. Customize a open source gallery software. You need to really customize and add some features that are not available in the original software. That will make your site unique. This is where you will incorporate your creativity. You can get your featured coded by outsourcing. 3. Promote, promote, promote.
Onera is right. There are lots of photo hosting sites already. Flickr, pbase ( popular with photographers ), peoples' own sites, and a million others to compete with. You can put up a photo hosting service, but getting people to use it will be an entirely different thing.