Picture 1) It's great, but the fog should be darker and maybe a bit more dense.
Picture 2) The lights make this pricture look really bad. Get rid of them. The fog is too bright to actually fog a person out like that. Make it Dark Gray atleast, then it'll be great.
Picture 3) Best one IMO. The sky is beautiful as well. Is it a custom sky or a backdrop? To make this look better, make more trees visable. You can barely notice any fog too, so maybe making the fog start/end increased/decreased would help.