Nice atmosphere and composition.
Mix wise I'd look at compression and EQing things, as well as placing things in more positions in space, both near and far, and L/R. Near far is accomplished with wetness and delay - closer things have more delay because they're close, so you hear it and then the echo follows a little later. A lot of mixing is about creating an illusion of space to make things sound clean/clear.
Nice work though! :)