After looking at the fantasy section of Hirst Arts molds, and seeing how they make a whole doorway that can sit on top of tiles, and be picked up to remove it, I came up with an idea for making a doorway with a door in it, that can sit on top of the industrial edging of a corridor, so a whole doorway can be inserted onto the map at any location. (again, these pieces are just balancing on each other, not glued, so that's why things aren't held together precisely). The sides and top of the frame would be a single glued-together object, that can be picked up and put down at any location on the map to add a doorway. The two doors could then be sat in it or not, depending on whether it was open or closed!
Also, being the impatient me, I looked through all the floor tiles I've done to find one that looked dry, and did a test paint of it. I tried a couple things. First, I painted metal and washed black. It was a lot of wash, and it still didn't black up the holes well, so I used tissue to dry it up, and once fully dry, I tried again. This time I coated it black, then drybrushed metal over the top. However, I'm not the greatest drybrusher, and some of the metal got into the holes. It looked okay, but not how I wanted. So then I tried method 3 which I will probably use. The idea is undercoat black. Drybrush metal. Then with a small, round tipped brush, I place a black blob of wet black paint in each hole. The paint, thinned a bit with water, spreads and covers the bottom of the hole, making it stark black against the metal brushed top. I really like the look of that, and it makes the shape of the grill really stand out, so that's what I'll probably do.
I also thought, why not paint some of my star wars figures with metal bases instead of black bases, so they blend in with the floors, and tried that out. It looks good, with metal base on top of a metal tile, so I think I'll do that for a bunch of stormtroopers and rebel soldiers for when I'm star wars-ing.
Anyway, here's a pic of the sample tile. It's a pity you can't see the glintyness of the metal paint in a photo, as it looks very metallic in real life.