Generally, I’d say your right. Most remodels use three patterns, floor, walls and accents. You must be very careful with accent tiles though, as they have the potential to date your remodel very quickly. Personally, I really don’t like different patterns meeting so I’d either use a plain tile with a patterned one or use one pattern everywhere, but vary the finishes (matte on floors, gloss on walls). Running your countertop material up, to create a vanity backsplash, is also an option. If you want a general rule of thumb, the more variations in patterns and colour, the busier and less restful a space appears.