Some restaurants focus solely on the food. The decor is secondary and not of much concern to the owners. However, more modern eateries will often have a specific and unique theme. In these cases the atmosphere is as important to the eating experience as the food itself.
There is a chain of restaurants in the US that have chosen the medieval era as their key theme. Patrons are treated as if they are kings and queens. The waiters dress in historical outfits and speak in an old English vernacular. Not only that, there is also a live show where men dressed as knights joust on horseback. This is a great example of how to do a theme right.
Other places decide to be more low key. There are a number of restaurants on the south coast of England that also choose history as a theme. The towns they reside are in linked to smuggling of the 18th century. Therefore the decor is made to represent this era. Some of these eateries also have paintings depicting the exploits of local smugglers.
Some restaurants have different twists. There are a number of places in Asia that serve food exclusively to cats and / or dogs. These restaurants are increasing in popularity due to the high number of people who have these pets.
Other eateries base their theme around popular cultural. There is a restaurant in America that is a real life replica of the Max, an eatery seen in the teen sitcom Saved by the Bell. This shows that an eating establishment can base their decor on anything. The only limit is the owner’s imagination.