I have one! Build a big temple where the whole floor is a mirror (basically just flip the build upside down and put glass between them) for the roof do a big dome (half sphere) and on the inside on the roof do sun and moon with stars. In the middle you can build a big tree.
Just an idea
There are a lot of good builders on here to take inspiration from, it's how I get my inspiration sometimes by just asking to see what they're working on at the time and getting some creative juices flowing.
Good luck on your adventures and I can't wait to see your build!
I don't build too often due to my lack of skills but I do practice art in real life so I can understand the frustrations of not being able to come up with concepts, something I like to do is keep an "inspiration" highlight on my Instagram. I save things to it that ether interest me or get me to think, this can be done with a folder on your computer or anything for that matter. That way you can look back at things you've liked recently or in the past in order to help get some inspiration juices flowing.
I personally like builds where nature is taking over the structure, this might be a bit over down but they are still some of my favorite concepts. I also really enjoy water based builds such as; fishbowl, ocean, lake, river, pond, etc...