Coffee Bean & Tea Leaf uses a tin lay-in paneling system as standard in their stores if you're familiar. . I can get the spec if you want it. It looks really nice (typical interior picture below). I don't know if a grid-type layout is something you're after but if it works for you let me know and I'll dig up the details for you.
It does tend to make the space a bit darker and it changes the acoustical characteristics, but personally I think it's effective and distinctive - a lot nicer than a typical fiber-based lay-in-ceiling or that popcorn crap that you get in residential all over the place. I imagine it could be installed underneath an existing hardlid without too much difficulty (although you may run into vertical clearance issues depending on the type(s) of light fixtures you want and the height of the existing ceiling.
