SUBWAY SERIES: Instead of seeing a newstand in your local subway station, imagine seeing the pop-up shop of an up-and-coming designer or artist. Thestorefront.com, an online marketplace that connects designers, artists and brands with retail space, said on Monday that it has partnered with the New York Metropolitan Transportation Authority to offer retail square footage in the New York City subways. “Our partnership with Storefront reflects the MTA’s commitment to pushing the bounds of vibrancy in the subway,” said David Bosch, director of leasing and acquisitions for the MTA, adding that over 5.3 million riders travel on the subway system daily. “MTA retail spaces bring a unique foot traffic advantage to the Storefront platform,” said Erik Eliason, co-founder and chief executive officer of Storefront. A sampling of the MTA spaces include a 70-square-foot space on the uptown platorm of the 50th Street station, with an asking rent of $2,676 a month. A 94-square-foot space that was formerly an ATM vestibule at Grand Central Terminal is $5,830 a month and a 510-square-foot shop at the 42nd Street subway at Grand Central is $10,500 a month.