The first thing i did was make the neck joint look a bit more realistic by adding some green stuff then shaping it to look like a flexible connection. You can see from the picture below how it was and then what it looks like after.
The next part was to give the torso a bit more body ( pun intended ) I did this in three different ways. The first was use the back part of the 40k imperial guard vehicle search light. The second was the grill part from the 40k vehicle upgrade sprue. The third and easiest was the bottom part from vox unit from the 40k imperial guard infantry sprue.