This is a nice layout, don't waste it!
The things you need to complete this map (Yes, it looks unfinished):
1.- Pick a texture pack.
2.- make details acording to the shapes of the textures you picked.
3.- Voilá, it's easier than you expected.
Things you have to consider after picking textures:
1.- Don't use grey textures.
2.- Try to use more than 3 colours (Lights, textures, skybox, etc).
3.- Try to exploit all the posibilities of the pack you picked.
4.- keep it simple, simple can be awesome too, but something simple is not just someting without details, it has parameters too.
Your map will start to take form in a blink of an eye.
You can contact me on discor or irc too, ill be online the weekends, but not always, so if you can catch me, just talk to me and we can take a deeper look to you map online.