We have a small bathroom, recently redone. My opinion is that large tiles make a room look less cluttered, therefore more spacious, but small pale tiles would probably look more spacious than large dark ones. Mixed colours can look busy and therefore smaller. You could make some trial pieces on large sheets of paper, paint on various tile patterns, then blu tack the sheets to the wall, like the match pot concept. I found it helpful to visit a tile shop which had really big sample boards of the tiles, but even then it took us two whole weekends and many revisits to the same shops to decide. We ended up with "bumpy white" tiles about 1.5 ordinary tiles wide and 2 ordinary tiles long, broken up with one horizontal line of square "bumpy blue" tiles. The white ones came from Band Q and the blues from focus, the effect is fab and the tiles were quite cheap. Also small tiles means more grout to keep clean...