The More the Merrier
Avoid limiting yourself early in the process. Experiment with different types of unrelated objects (see Figure 2), even if they're not as familiar to you as your usual concepts. As you work with the various shapes, colors, and moods involved with different subject matter, you may discover new avenues of inspiration that you didn't originally consider.
Figure 2 Examine many possibilities when choosing your subjects.
Maybe a small animal or an infant can be the start of your vision. And don't assume that the subject is always an object in the scene. Perhaps your subject is the scene itself, with elements of your other shots blended in to create a surreal and impossible landscape. Turn things around. Look at a subject or scene from an unexpected angle or perspective, and see whether you can find common threads where you can start to bring things together.