[Avalaxy]

Start with the business model canvas. Look at the options you have per category (so for example: for revenue streams, list all the ways to make money you can think of, for value propositions list all the unique ways to stand out, for customer segments list the different types of user groups you can think of). Now pick a random topic that you're interested in, shuffle all the pieces around and see what new business model you can think of.

It's also great that you can then just hand in a business model canvas that explains your idea.