Not that a restaurateur can completely avoid any need for design this way, but you can certainly come close to spending almost nothing on interior design if you decide to open what some people call a blind restaurant. It usually means that patrons get to dine in complete darkness. Naturally, for vision-impaired people this does not present any problems, but for the rest of us the experience is quite unique. Typically, you will be ushered into the darkness and seated. Simple rules and precautions will be explained, then you are ready for a strange awakening of senses. It is common knowledge that in the absence of visual stimuli our hearing greatly improves. But the sense of taste and the ability to enjoy the texture of otherwise mundane foods also increases!
Dining in the dark is, of course, not something that most people will choose to do on a daily basis, but if you plan to cater to both the blind community (who, obviously, can work as your waiting staff!) and the general public in a large metropolitan area, why not consider this idea? There are also additional features that you can try to introduce. Berlin's Nocti Vagus restaurant has the following list of extras: "Live music, Dark Theater, Comedy, Erotic Evenings, Creepy Story Evenings" etc.
A few restaurants of this kind (I believe that The Blind Cow was the original blind restaurant):
Dans le noir (Paris, France)
Dans le noir (London, UK)
Nocti Vagus (Berlin, Germany)
Opaque (LA-West Hollywood, CA)
O.Noir (Montreal, Canada)
The Blind Cow (Zurich, Sqitzerland)