As I understand it, it seems that “un espace design” here means a place reserved for Design exhibitions, it generally is placed in a store where consumers can look at new and innovating products.
Design exhibit area should do it.
Or maybe the longer alternative design-themed exhibition space
The obvious English appearance of the word design gives it a distinctive recherché feeling that design in English just doesn’t have. Designer used as an adjective comes a lot closer.
In this context, espace is an exhibition hall, typically a building comprising a large room with temporary booths that people wander around. Designer space is actually not far from the mark, but doesn’t quite sound right in English. Designer hall? Designer exhibit?
This article about an “espace design” in Montréal translates the expression with Designer studio.
In that context, the author just wants to emphasize that the exhibition place is decorated in a modern and creative way, what is familiarly called “design” in french.
Like “un meuble design”, “une voiture design”.
It just means that the particular object which is “design”, express creativity/modernity