Depth, bumps, things for the brush to catch onto when drybrushing.
I'm starting to think that the peacekeeper outpost is starting to develop a bit of an anime vibe with it's straight lines and rounded corners...not that this is a bad thing.
But it's looking a little too clean and smooth. Perhaps if these things were dropped from orbit, that might be a good thing, but I'm thinking more of the original design when I see these outposts shipped by truck, helicopter and barge. It still needs to be relatively smooth, but can handle a few bits of relief work across its surface.
To do that, I use cardboard.
In this case I draw up a few strips, some rectangles of various sizes, circles and a star for each side of the structure (in keeping with the stars on certain figures and the stars I've drawn on the bases). These are cut out with a sharp knife.
The MDF material is actually very similar to cardboard, but much thicker and bound with a harder glue/resin, so gluing these cardboard components onto the structure. Simple PVA/Wood glue does the trick.
First the pieces are laid into position, then they are glued down one by one. To ensure a good bond, I'll typically place some greased/baking paper on top of the glued pieces then a heavy board or book. This makes sure the card sticks to the appropriate surface with a flush join.
The long stripshanging over the edge are folded around the structure and glued throughout. I think this gives the whole form a more unified appearance, rather than just looking like flat panels thrown together.
Some components are built up in multiple layers before being applied to the structure.
Here's where the project stands at the moment.