LOS ANGELES — Four months after merging with Starwood Hotels and Resorts, Marriott International is starting to put its stamp on the brands it has acquired.

The largest hotel company in the world is taking two of Starwood’s brands, the boutique Aloft and the eco-conscious extended stay Element, and testing out new design and food and beverage concepts.

Marriott has an “innovation lab” at its headquarters in Bethesda, Md. In October, the company unveiled its first M Beta hotel for its flagship Marriott Hotels brand at the Charlotte Marriott City Center. Marriott will unveil a temporary innovation lab Monday at the Americas Lodging Investment Summit in Los Angeles.

The company tries out new programs and products at the functioning…