Tile Format
In either case the format and color of tiles can be used to great advantage with a little imagination. A bathroom revamp is not something normally done on a frequent basis so it is advisable to select size and color in line with current and projected trends to keep the bathroom as modern as possible, for as long as possible. Over the years the trend in tile format has been to increase both dimensions following the rectangular pattern. By comparison to 20 or so years ago when the norm was square 10 cms * 10 cms (although this format is still available). It is now common to encounter tiles in the 30 cms * 40 cms range and not unusual to find tiles of 30 cms * 60 cms and larger. So, potentially a good choice would be the larger format. Be aware that the small tile offers the advantage of being able to 'follow' the contours of the walls much more so than the larger formats.
Use of Color
Color choice is of course entirely subjective again current trends favor lighter warmer pastel colors. The use of these colors increase the perception of space and light, especially in a small bathroom. Colors such as beige, orange and pink would be regarded as warm as opposed to blue, green, gray. Tile arrangements range from the simple one tile for the whole walls, to more elaborate combinations of tone used with a border tile to enhance the effect. Commonly the darker tone is used below the border and the lighter above. One border or multiple borders can be used. Picture or decorative tiles can be added at random but focal points to further enhance the desired effect. Tile sets are available from manufacturers that offer all these options.
Tile Patterns
Not only color combinations but combinations of tiling patterns can be used. Such as diamond pattern followed by a border and then a simple rectangular arrangement. Floors can be equally creative with diamond, square, rectangular and brick work patterns. If using a rectangular tile, aligning the longer tile dimension with smallest room dimension tends to expand the perception of that room dimension. The reverse is equally true, and in this manner a bathroom can be made appear wider or narrower. How much pattern effect could be used to achieve an optimal result would depend to a large extent on the size of the bathroom.