What artistic feature became prevalent in the margins of paintings under Jahangir’s patronage?

Highly illuminated in gold with flora and fauna

Answer:  Highly illuminated in gold with flora and fauna.
The margins of paintings under Jahangir’s patronage were highly illuminated in gold and embellished with flora, fauna, and sometimes poised human figures.

In contrast to the Akbar’s atelier, where the works were mass produced, Jahangir’s atelier gave preference to a lesser number and better quality of artworks produced by a single master artist. The Muraqqas individual paintings to be mounted in albums became popular under Jahangir’s patronage. The margins of the paintings were highly illuminated in gold and embellished with flora, fauna, and often poised human figures. The war scenes, portraits, narrative and storytelling prevalent in Akbar’s style were overtaken by minute details and refined rendering of lavish court scenes, aristocracy, royal personalities, as well as, character traits, and distinctiveness of flora and fauna