I don't know...it's classic for a reason ; ) . You could play around with scale, like oversized hex tiles or pattern, maybe run breadboard horizontally, or put it on the ceiling. I'm leery of putting too much personality in big ticket items like tile, but there are awesome "subways" in different colors and sizes.
Good luck, post pix!

Different tile on the floors? Basketweave, Text, penny rounds...

A pencil liner tile in different colors in different baths?

You could easily have a common thread running through with different elements in each.

Here is a link that might be useful: Nemo Tile

We just recently finished our bathroom and I'll be posting pics soon. We wanted a "white" bathroom with subway tile wainscoating. We love the look of marble, but we wanted something that was warmer and a little less formal looking. We decided to use a wood countertop and travertine floors. We also used a slightly off-white subway matte finish subway tile to "soften" the look and feel. We used larger format tiles on the floor and a herringbone pattern on the shower floor. Picking the right tile was difficult, but we found an "ancient" tumble travertine that is perfect for the look we wanted. We are extremely pleased with the finished look. It achieves the clean, fresh feeling of a white bathroom, but its also warm, soothing, and has a subtle warm energy to it. I'll probably be posting finished pics this coming week if you're interested in seeing it.