Ist es möglich mit KI Bilder in 16k oder mehr zu erstellen, also wenn möglich mit Flux?

You can do that in principle, but why should you?

1. What kind of device do you want to let the pictures display that you think you need such an absurdly high resolution?
2. To generate an image natively in such an absurd resolution, you need a lot of computing power (RTX6000Ada and most of it you can afford) and a lot of RAM and VRAM and a lot more patience. No online AI provider will allow you such a project, which means you need to host the AI itself.