Don't mix brown and grey tiles. That's probaly the worst thing you can do. Try not to mix diferent tiles too much, use on texture as 'main tile', like the Deimos for example, where most of the ship is covered by just one texture(Why would y ship beeing covered by 10 different looking armor plate types? this just makes the ship look like a collection of repairs which is ready to fall apart).
Try to use a texture where the lines between the armor plates aren't too obvious, like the tiling texture on the Deimos corvette for example, because if you could see the spaces between the armor plates from a mile away I think that ship would be in real trouble.
Don't overdo the tiling. Rather choose a low tiling where the texture looks a bit more blurred but less repetive, because most of the time you won't skim the ships surface and it looks better than having the texture repeated a hundred times over the ship just to make it look sharp at close.
