Hello!
This map is honestly soo cool! and yes it is quite hard xD, I think it has a lot of chances of being accepted! To upload a snapshot, write a comment and click upload a file!
Good luck!
I think that an interesting theme would be simply "Minecraft" as it could be interpreted in many different ways. With this broad theme, all builds will certainly be very original and different as for this, anything could be built. With a theme like "castle", all builds would be castles...