Do your research, find your references.

Good designers are not naturally talented artists that can come up with creative ideas own their own...

They all do their research, and grab references to inspire their ideas..

When you are researching you are NOT trying to look for features that you can take and put also into your level.

You are looking at how the environment looks like, and you want your environments to look and feel similar to those environments.

Since everyone is going to begin meshing up the level, it is extremely important that you try to mesh your map into something that actually looks and feels like what you described in your narrative.

If you are building castles, make sure you research structures of castles.
If you are doing warehouses, make sure you know exactly what warehouse looks like.
If you are doing Jungle ruins, then what are the features of jungle ruins.

If you are doing your research, then you might want to do abit more research, because no maps at the moment seem to have the full essence or feel of what it is meant to be.

Reference does not mean grabbing ideas...
Reference means you really want to create something similar to reference!!

The major marking criterias for your maps are

30% Fun
30% Fits with Narrative
30% Principles Applied

So make sure your map actually makes sense to the narrative. And you can still make changes to your narrative, but in the end, i will read your narrative, and see if your map actually feels like what you have described.