Looking good for a modern level, modern tilesets aren't the easiest to work with.
From what I can see you're on the right track, you just need to work on your walls and try to make it look a lot more realistic. Try to not make the surrounding walls so wide, and also make them even width all the way around.
I also think you need to focus on making your flooring a little more exotic and not so predictable. There is nothing wrong with the tiles you used, but just practice different patterns and styles.
Below one of my levels I created with a modern tileset, I never got the chance to finish it but maybe you can get a little idea on different ways you can make an inside.
my crappy unfinished level