Finally I found an awnser:
NOTE: This is only for Mac, I don’t know how to do it on a Windows machine.
1. connect your iPhone to your Mac
2. close the starting iPhoto for the last Time 😉
3. open up the “Image Capture” (eng) / “Digitale Bilder” (de) Application
4. select your iPhone and choose “No Application” in the DropDown List.
5. close it and enjoy connecting your iPhone without the annoying autostart