With most of the answers to these 4 questions I should (hopefully) be prepared to start building my first showcase!
Thank you for reading and happy building 
Aebics.
Hello, I can give you some advice from my own experience. I actually started working on a showcase too, and nothing motivates me more than thinking how cool the final result will be. Depending on the style of the showcase, you can find inspiration in nature or simply by going for a walk. Depending on the building skills you have, you can choose a nature-styled showcase if you don’t have so much experience or even a dirty city representing how cruel the humans are on nature, your choice is yours! Hope I helped you and good luck!
A few of these questions has been brought up before regarding (inspiration, motivation,).
When looking for inspiration it can come in many ways, whether it’s come to things that interest you I would try finding things you enjoy creating find things that inspire you and use that. I’ll visit different types of sites to get inspiration of things you like to create as a first showcase Pinterest, poly count) or images on google it’s always good to look up reference images of the things that inspire you.
What you can do is go outside and takes pictures of the things you want to create you can either write down ideas to add when starting a showcase take a few pics of things you want to create as a showcase, architecture designs, london structure buildings ect. The build style really depends on your overall preference there are variety of showcase that hold sorting styles.
Here is a thread regarding around motivated and advice starting a showcase, it may be something to take along the process.