Here's a closeup shot of one of the smaller "floor" components. The basic body is part of a Matchbox Mega Rigs toy. I attached this to a base made of 2 1/2 inch wide Lexan (strong stuff!) as I do all my hulk hallway sections, for stability and durability. I added cross stitch mesh to the base to simulate floor grid. I added some Armorcast pipes and some computer components to finish off the piece. You can see the piece from a top down view in the center of the picture below.
Here's a top-down shot of all the Space Hulk scenery I've made so far. The two hall sections are on either side. The big floor section is at the top. The Pipe terminal piece seen in the photo above is in the center, and a similar piece at the bottom is also made simply by basing up some Armorcast pipe bridge pieces. The two short hall sections are both made from computer case pieces, based on Lexan again. The nice thing about using a consistent material for basing is that your components all have the same floor height, and tend to be more stable when based. It is worth noting that the wall piece on the right is considerably more banged up than the one on the left, better for representing ancient sections of a hulk or the forgotten bottom maintenance decks of a ship, or decaying sewers. To rough it up, I bent a number of edges, especially floor grating, and used a grinder wheel on my moto tool to put loads of nicks and dents all over. I used a lot more brown and rust colors while paintint it also.