If you want to create an image host website you don't need so much resources. It is ok for start if you have a server for main site(including sql) and an external server for hosting images that doesn't a lot of bandwidth and resources.
For Streaming website, you need one server for main site(and sql) and anothers for streaming. Personally i think that the main problem will be the bandwidth because you will need to support multiple users downloads. If you want to share hq (720p-1080p) movies you will need for start up website, at least 1 gbps dedicated bandwidth and some good resources for the servers where you will host files.