Well this is the problem third-party services are the most convenient but can be recalled at any time, so perhaps serverside is the way to go. It's just a case of finding the right mod to suit as there's user galleries, individual uploaders, ones that use third parties. I'm thinking just a simple upload one might be best but then the galleries would be good for Photography. There's also one that interfaces with Coppermine but I've never used that, so can anyone shed some light on it? I think matt5cott has used it before on his sites but thats about all I know.