How to implement a System like this easily using Altera Tools of my DE1-SOC?

I would suggest staying away from usb for now. It is a very complicated protocol and I don't think there are any free cores out there. I think you can get ethernet for free but rs232 it's the easiest to implement yourself. From this you can easily load an image into the on board ram.

Streaming means data is streamed into the design. This would usually mean delivering the pixels one at a time and your design keeps track of which pixel is being processed. This means you can build a pipeline which is much more efficient then read/modify/write operations.

As for clock speed, this is up to you to decide. There is no "standard". Clock spotted is dictated by your interfaces or data rate requirements.