12/10/8/6 maybe? Or larger.
I was thinking maybe a 14, 10, 6, and maybe a 4? I don't know. The ledge is a pretty nice size.
If using the cake knife and server as a scale, the table looks to be about 4'. My guess is that it's sitting on an 18" cake stand, with the cakes being 16/12/8/4 - or perhaps 18/14/10/6 - in any case, it looks like the cakes drop in 4 inch increments.
16,12,9,& 6 maybe
Thanks everyone! That helped me give the bride some educated choices for cake.