You could really benefit with there being many more of these mines - if just the one then it doesn't fit well into the composition. There's a lot of space in the image and it happens to be behind your character and it makes the composition look a little awkward (referring also to your statement on it changing her silhouette). I also agree with 3dc in that it could do with having a bit more atmosphere between that and the character.
@3dc Alt hair. Still not totally sure.
Nice, the mob guy somewhat floating seems a touch odd to me, it looks like he was just thrown in (the water) and idk if mob guys and pirates where in the same time-frame. (love the idea though seems like a fun active time frame.)
Him floating in place though (idk if cement does that over time?) maybe put something under him or make it feel landed in the scene. (please keep in mind i don't do this stuff i am just suggesting what might look good to help you finish it up, otherwise) this is looking better and better.
@3dc She's meant to be hunting drowned souls for Davy Jones, so I'm just going through all the types of underwater dead I can think of. (She's a punk in a leather jacket with dyed hair and a metal t-shirt so I'm hoping people think it's set present day.)
I'm going to add more lost souls in the background time / room permitting, just wanted to get the focal bits done first. The cement shoes guy I was thinking could move around despite encumberment like other ghosts. I can always just stick a bit of rock under him if it's confusing.
Other underwater undead ideas from anyone would be appreciated.