I'm partial to ovals with maples, and blue and cream colored glazes will usually work. By the way, I think those pots are all too big. The depth is ok, but could definitely go shallower, and the pots are too wide. Depending on the depth of the pot, I'd be looking for something around 16 to 18" wide.
I also have a soft spot for light blues and creams with maples. Honestly, it's so hard for me to find the "right" pot without having the tree and pot next to each other. That said, I would be looking for an oval. And don't go too cheap, you have the makings of a nice tree, and it deserves a nice container! I constantly see nice trees in crap containers at local shows here and it drives me nuts.
The current mustard pot is 17" wide and 4" deep. That's why I selected pots that are around 21" wide and 3.5 deep. The tree is around 24" tall now and would end up being taller with an apex.