Create a global field with the images you require. Make that field show repetitions for the maximum number of tables you might require. Paste or insert picture your images into the rows of the field. This field should probably be in your tables field or somewhere else accessable to all tables records.
Now what you have are images which can be shown or not shown by calculation... just by referring to the repetition number in your calculation.
Now... each table is either booked or unbooked... but may also be not set up.... for each sitting at the restaurant. They can be shown an hidden or colour coded... I can imagine many things you could do.
As far as images go, there are many free libraries of images out there which would have the necessary pictures of furniture you would require... just search google.