at this stage you just need to keep working on the fundamentals.
Do master studies, lots of them. Read some good books like James Gurney Color and light and paint from life as much as you can. Most generic advice ever, repeated over and over xD but still true.
To me it seems like you just need to study a lot more. If you want to improve this piece, then study rocks, study cities at night, study humans and drapery. Study, understand then come back to this piece. You will see all what you were doing wrong by yourself.
First off I have to agree with EduardoGaray, you need to study fundamentals. As EduardoGaray said it is a repeated comment but thats because it is so very true in most cases.
I did a quick and dirty paintover for you. One thing that would help with your aim of "large scale" would be making the structure a little smaller. This seems like a contradiction at first but it gives you room to show just how big that building is in comparison to the environment around it. Another thing is the light source from the door travels so far that it makes the structure look small.
I could go on but as EduardoGaray and I have said its just down to study at this stage.
First of all, there is some story behind your art piece, that's good, something is going on.
If you paint scenery like this, I think you should start your work with value planning: http://www.youtube.com/watch?v=x6BlTEytocc
It will give your painting nice depth and readability.
Have fun!
It's a somewhat solitary existence, a bit like a lighthouse keeper throwing a beam out into the darkness, in faith that this action might help someone unseen.
You should think of planning value even more. I did a quick paintover. If you want a pitch-black night, then the things nearest to the "camera" should be the brightest. Things in between should be in the middle of birghtness and background should be the darkest. It will give you the feeling of space. What's more, the foreground should have the greatest contrast, where as the values of background should be close. When you plan your values stick to their range. Do not use highlight values from foreground on background etc. Of course, it's your piece of art so you can do whatever you like. Have fun with it. :) What I have written is just the way I would see this picture. :)
EDIT: Made you a quick thumbnail of what I mean.
It's a somewhat solitary existence, a bit like a lighthouse keeper throwing a beam out into the darkness, in faith that this action might help someone unseen.
Well, I just wanted to push the design forward and add more focus on the foreground, you can go ahead with Mike's aproach if you want to have to focal point on the cave entrence. Or mix them both in the way that you like. :)
It's a somewhat solitary existence, a bit like a lighthouse keeper throwing a beam out into the darkness, in faith that this action might help someone unseen.