The icons are in a 16x16px grid, but since they are different sizes - some are large objects, some are small, the larger objects take up multiple grid spaces. If they are too large to fit into 16x16px they are centered on the next smallest tiles they can fit in. If you need it in some other configuration you will have to do it yourself, as I can't make different layouts for everyone, as I don't know what everyone needs. 