10-11-and 12 in advance map are usually available to use and won't affect any of the other tiles except the secondary tiles that you're probably going over anyway. So for example, Cerulean City, if you insert new tiles and change the pallete of 11 and 12, the blue houses and the orange top houses will only be affected. You could ask Aryan143, I believe he knows more about tiling not too sure.
Hey, got a question about tiling. There is this blue house that I want to insert and it takes up all 16 colors. Which palette should I insert it at and what should I do for other tiles that might be affected by this pal change?