I think if the object stood on some lighter surface, for example on the floor, and a shadow would fall from it, it would look better. You can also darken the color of some elements. For example like here:
So this is kind a general question but also specific to this project. I want to take WIP renders of my models but usually I find they turn out boring without materials or texture. A lot of advice on the topic I've found, of improving renders, is for finished renders. I've tried to adapt the advice but not having much luck.…