Thank you for the detailed feedback anomie - exactly what I am looking for when I post here.

-I'll take another look at the whirlpool when I get home and am back on my normal computer - perhaps its not as bad as a I thought.

-The rivers and pools of blood will all be included in the final map. The previous rivers/pools were just colour-blocks as I worked on other parts of the map, then I finalised the blood texture. Now that I am working on the pool and river banks, I have put a layer mask over the blood texture, and am bringing it back slowly as I do the banks. I still have not decided how to do the rivers yet.

-regarding the something 'not quite right', I have looked again and actually I think that I agree with you. Perhaps this is because the wall texture has a hollowness to it. I am going to try and darken it slightly by overlaying the walls with a 30% burn layer of pale pink, and maybe it will fix that. I'll post that up tonight, along with another couple of pools.