You’ve seen many paintings of the last supper before, but probably not like this. Which is a pity. Because it is true that Jews at the time of Jesus actually reclined at tables.
Consider these verses from the gospel according to Luke:
When one of the Pharisees invited Jesus to have dinner with him, he went to the Pharisee’s house and reclined at the table. (Luke 7:36)
When Jesus had finished speaking, a Pharisee invited him to eat with him; so he went in and reclined at the table. (Luke 11:37)
When the hour came, Jesus and his apostles reclined at the table. (Luke 22:14)
I had always wondered how they reclined. As always, a picture tells a thousand words. You will see more paintings by this artist, Rod Borghese, at Jewish Jesus Art.