At a time when so many museums seem intent on new spaces for new design and new art (like the Whitney, Upper East Side deserter), it’s a relief that the Cooper Hewitt finally spent the time and the money to make their 1902 Carnegie Mansion sing. Rather than being a straightjacket, the mansion’s ornate rooms and halls now form a rich and idiosyncratic frame for design objects of all ages. Gluckman Mayner and Beyer Blinder Belle worked together on restoring, updating, and adding to the architecture. The cases, designed by Diller Scofidio + Renfro, are crisp and clean, designed for sightlines and visual connections across the grand salons. The firm, as it did at Lincoln Center, has also jazzed up the outside: a new typographic canopy on Ninetieth Street leeeeans toward Fifth Avenue, and there’s L.E.D. lighting on the granite piers out front. Another example of new and old meeting in an elegant place is Boym Partners’ rendering of the mansion as emoticon: architecture transformed into “#”s, “+”s, and “”s, and applied to mugs, playing cards, and notebooks.