Tile can be tricky...with a capital T! For larger bathrooms where you don't want to have the same tile throughout but have a lot of area to cover and aren't sure how to mix and match, this design dilemma can be daunting. Tile is great and can make a huge difference in any space, so once you're comfortable with putting it together, you open up your home to so many new and interesting design possibilities.
As with any space, the goal you want to achieve with your final visual is balance. This applies to anything applied to the wall or floor too. You never want a room to feel too heavy on one side, top, or bottom---everything should flow. This feeling is what evokes satisfaction when entering a space. When selecting tile and deciding where to apply it, you want to achieve balance. If you have a wall tile that will be in the same room as floor tile, make sure the scale varies. Too much of a small tile will look all very busy, especially if it's concentrated in one space. And too much of a large tile can feel heavy, if it's applied to the wall. So mix it up! Small tiles on the wall with larger ones on the floor will provide your space with the applications it needs to finish it off but won't overwhelm the room.
Now that we've got size figured out, lets discuss pattern. Pattern is ok, but don't go overboard. Remember, tile is a commitment---you're probably not going to be replacing it every year so you want to make sure there's an element of timelessness that will make it transition well as the rest of the decor changes. So, if you're incorporating pattern in one area, try balancing it with a solid in another area--ie, wall & floor. Usually the floor is the best place for something solid, but it's not necessarily a rule. A large scale, bold pattern on the floor coupled with a smaller, solid pattern on the wall is still visually unique and balanced.
When it comes to stone, you have a little more flexibility. Tiles that are patterned or printed...or anything with glaze need to be treated as a pattern, but natural stone can be viewed as a neutral. It may have it's own natural pattern in it, but because of the organic feel of this type of application, you don't have to limit yourself so much. Try messing with the scale of pattern when incorporating natural stone---you may have a tile with a naturally small scale pattern whereas, it's coupled with another stone application in the same room that's much larger in scale. Normally large scale pattern in natural stone is much more fluid which we love!
Don't forget about tile finishes as well. Adding variety in something like this can not only help keep a space balanced but also add a unique high-end look. Matte finish is all the rage now--we've moved away from the "everything has to look shinny and glossy" era and moved into a more organic feeling trend. The flat or matte finish tile goes perfectly with this so don't forget about that option.
Finally--don't go too crazy with color. This sort of goes hand-in-hand with the pattern statement as well. You want your tile to last a little while so don't go too color trendy when you're selecting something. Be sure to have an element of neutrality that allows your space to stay transitional.