Yes, the sentence is grammatically correct.
The sentence means that the speaker has come across an image that they feel perfectly represents or embodies the concept of being "unaware." The word "caption" suggests that they intend to provide a label or description that reflects the essence of the picture.
Here are a few possible rephrasings:
1. "I've finally found an image I can describe as 'unaware.'"
2. "I've come across a photo that I can


