the colors dont look as good in the 3rd image
As for the overall building, it looks empty/hollow because you didn't give it a floor and it could use more details, scenery, plants, etc. It looks like a good design for a strip of shops. It also sort of looks like its just a roof top, but kind of lacking in height (just my opinion). Height is all about preference, I just think a coaster should have tall scenery around it.
There are lots of pics/vids out there of some really good designs, but my suggestion is to try raising your station platform higher so that you can give the building around it some height, so buildings can be tight around the ride/queue instead of stretched out all flat like, that's just my view though everybodys can be different. Another idea is to try and keep most of your queue line within the building, possibly. It's all up to you though, and how much time you want to spend on that one coaster.