There is no bad tile choice for a kitchen splashback. However, you do have to consider the ease of cleaning. A smooth tile will a larger surface area is easier to wipe clean of grease and cooking fats than a structured tile with a rough or small surface space—the smaller the tile; the more grout to keep clean.
In terms of trends, feature tiles such as mosaic and subway tiles are certainly the most popular tile choice for kitchen splashbacks. They can be laid in an array of patterns and come in various shapes and sizes. Mosaics are traditionally square, but today, they are available in many shapes, including fish scale, penny (round), hexagon, finger, herringbone, to name a few. While mosaics are more difficult to keep clean, they continue to be an extremely popular choice.
Both feature tiles and subway tiles are available in various colours and suit just about any design style, partially subway tiles. Subway tiles are potentially the most popular due to their versatility in design and endless pattern possibilities. They are also much easier to keep clean than mosaics.