Back in Windows 8.0, tiles can be either small (smaller) or large (larger). Now in Windows 8.1 Preview, a tile can be small, medium, large, or wide. Small tile does not show application name at all, so can be confusing if you are not familiar with the applications. Medium is what used to be the "smaller" version and Wide tile is equivalent to Larger. Large is one of the new sizes. See below for screen captures showing different sizes for Desktop tile.