display space dust for acceleration
The background already displays the movement. Some space dust (you know, these the tiny dots moving around ships in other space games), could also display acceleration relative to the reference body.
It would give a feelling the thrust and attraction.
With 0 acceleration, no space dust would be visible. With high acceleration, more would appear (and maybe leaving some trails).
Rem : it is a display of acceleration, not forces applied to the ship. Thus, no space dust would be displayed to a ship landed on a planet, while some dust would be shown around a craft in orbit.