Your restaurant is a good start, for know just like @greatgavin said what style and theme are you going for so others could know what restaurant your going for. Here is a couple of things to add to your restaurant to look more decent!!
Restaurant
I have notice that your restaurant, doesn’t have that much details to it however most restaurant have different kinds of floors and. Walls you could maybe! change the floor to a more wooden material and add some more windows and dividers on the building and add some potted plants, shelves, chairs, tables, lights on ceiling, ect. To look more decent and have more open space to. Add more details to it and as said above, you could add one of those “Host Stand” near the door and add different seating like booths placed, down in other areas!! and for simple restaurant, you may want to inlcude some seating outside a, sign, menu…
Inside Design
If your going with a more smaller restaurant. Add some tables, chairs, pictures, potted tree plant, trash can ect. I would recommend you add some details onto the tables like some napkins, salt shakers, pepper shakers, plates, forks, knives, glass cups, little details. And add one of those white table cloths under the awning to look more like a restaurant! however on what style your going for consider looking, at different restaurants. To get a idea on which theme you want as said above American, french, fast-food, italian,?
Front Design
In the front of the restaurant. I would recommend you add some little bushes, flowers, rocks, trash cans, grass, ect. And for the windows on the front of the building! make the windows a little tall and divide them. I would also recommend you add some lights, on the front of the building and the inside add lighting in different. Areas that is spaced out all over the room part!!
Overall, good job on your creation hope to see the final build, from you very soon.
Kitchen
Some details to add in the kitchen area, if you implement that into your restaurant include some: Freezers, fryers, ice machine, oven, ranges, work tables/stands, sinks, holding cabinets, refrigerators, oven griddle, steamers, grills