I want to create modules on Wordpress to teach people how to run a retail business better in a small niche fitness studio.
Blog topics are going to be limited to what your customers are interested in, and I'd say specializing those topics to fit within your niche is getting creative enough for them.
Beyond the topics themselves, though, there are a lot of ways to get creative, but they all center on the same kinds of principles: Taking the same-old, same-old and changing something about its delivery so it becomes more artful. Once you understand that, you won't need anyone to suggest a topic. You can simply take any topic and make it your own.
For example, instead of discussing a topic in business terms, use a different scenario altogether, like a game or journey that parallels the challenges fitness studio owners face.