Hi, the best shop window designs come from understanding your brand. Who is your core customer, what is your value proposition to them and how is that different from your competitors. Once you have clarity on that you can begin brainstorming the right 'messages' for your store front to communicate.
When you have that clarity, I suggest searching pinterest for inspiration. The creative part of shop window design is very specialised and the people who are good at it are extremely good. Using Pinterest you can learn from the experts, find inspiration and ideas and then either put it together yourself or talk to a digital/merchandising company to get their help.