For me, creative imagination in design is more of a process than anything else. It is taking the elements of a design idea, and recombining them into many different and new ideas, such as designing a ring.
Many people will have a style of design that they tend to stick with. "Their personal design motifs" that they always tend to do. The creative part is to break away from what you have done in the past and design something random.
Will these ideas work? maybe, or maybe not. What you like or not like as a design may be different than the person next to you.
Throw what is considered "acceptable" out of the window and try ideas that are foreign to you.
These ideas of design will lead to a flexibility of thought that allows you to see even more possibilities.
Imagination by itself can stagnate. Creative imagination leads to innovation in design.