Isn't that an awesome photo? I took the Fenway Park tour earlier this year and learned a bit more about it. The photo depicts the D'Angelo brothers; two twins that started a souvenir business in the streets outside Fenway Park in 1947. There they sold mostly pennants and other merch from a street cart. Eventually they opened a brick and mortar store along Jersey Street that stands today and functions as the Red Sox's team store.
Today the company has re-branded under the name "'47" and they offer all kinds of sportswear for MLB.
As best I can tell neither TEI nor '47 made their own pennants; they used an outside supplier that, based on this 1968 photo, appears to have been Trench.
Here's a contemporary photo of the store's interior showing the very same wall--with one or two less pennants for sale
