Yes, you should be using the non-free image for most x86_64 hardware. On newer system we are increasingly seeing issues with StartOS 0.3.5 missing the graphic driver. It looks like that is what you are running into. The soon to be in beta StartOS 0.4.0 likely solves this issue. In the meantime, you can try the headless install method described here:
The gist of it is, if you don’t connect a monitor the the display driver is not needed. But you have to prep the system first.