Simple:
* She sat on the porch, lost in pensive thought.
* He stared out the window, a pensive look on his face.
* The artist's pensive expression hinted at the depth of her work.
With context:
* The silence in the library was broken only by the gentle rustle of pages and the occasional sigh of a pensive student.
* After the news, she fell into a pensive mood, wondering about the future.
* He spent the afternoon in a pensive state, reflecting on his life choices.
Figurative:
* The old oak tree, with its gnarled branches reaching towards the sky, stood as a pensive guardian of the forest.
* The city, bathed in the soft glow of the setting sun, seemed to hold its breath in a pensive moment of quiet contemplation.
Note: "Pensive" often implies a thoughtful or melancholic mood, often accompanied by a quiet or introspective demeanor.