General:
* Enlighten: To provide knowledge or understanding.
* Light up: To make something brighter.
* Brighten: To make something more cheerful or attractive.
* Clarify: To make something easier to understand.
* Explain: To make something clear.
Figurative:
* Inspire: To fill someone with creative energy or ideas.
* Reveal: To make something known or visible.
* Show: To demonstrate or make clear.
* Elucidate: To explain something in detail.
Specific to light:
* Beam: To shine brightly.
* Glimmer: To shine faintly.
* Radiate: To emit light.
The best synonym for "illuminate" will depend on the specific meaning you want to convey.