A long theme could be 'The Cycle of Life and Death'. It shows how death is intertwined with life, like how the death of one organism provides nutrients for new life to grow. In nature, a fallen tree decays and becomes the soil for new plants. In human society, the passing of the old generation makes way for the new, with new ideas and ways of life emerging.
The theme 'Death as a Great Equalizer' is a profound one. No matter how rich, poor, powerful or weak a person is in life, death comes for everyone. It can be used to tell stories that show how in the face of death, all worldly differences seem to fade away. For example, a king and a beggar both meet the same end, and this can lead to a reflection on the true meaning of life and the vanity of excessive worldly pursuits.
The theme of 'Grieving and Healing' is also suitable. Death often leaves behind a trail of grief for those left alive. This theme can explore the different stages of grief, from denial and anger to acceptance. It can also look at how people find ways to heal, like through sharing memories, creating memorials, or finding support in communities.