ive been playing with HDR recently but am still a noob - im not a fan of the "grunge" effect to be honest and i try to avoid it - i think HDR works best when you get all the detail but keep the light information.... but i think youve done it nicely on number 6 and number 1 - the others are still very cool no doubt but for me personally id prefer to see abit more light
whatever though nice find! pic 1 is by far the best though looks very creepy and haunting