The first level is going to be in a Star Shaped Castle so I have roughly sketched the level design using Inkscape. 

I struggled a little bit but as I was sketching ideas started flowing and now I'm ready to try modelling this in Blender.

A castle is so goddamn huge. I'm not even sure I'm skilled yet with Blender to make such a huge project but I have to try.

I've also set up the GitHub Repository, Created a Blank Godot Project and also chose the licenses for the project.

Assets I plan on modelling:

Medieval Styled Castle

Bricked Walls

Wood + Iron Doors

Silver + Golden utensils

Candle Holders

Paintings

Kitchenware

Dining Table + Chairs

Fireplace

Statues

Stairs

Throne

Royal Carpet

Curtains 

Flower Vases

Miscellanious Royal Decoration

If I succeed, you'll guys will be able to buy all of these assets for a very cheap price and use them in your projects.