I've built a lot of woodworking projects over the years as a hobby (never a table light...). One suggestion for a project like this is the hardware available will determine the size. In other words, figure out what lights you want to use, buy them, and then design the box to hold them around them.
If you have the room and the money, a lighting surface that matches the playing surface of the table is very nice. The expensive Diamond light and the Brunswick GC light are both very close to the table dimensions.
Good luck.