The Sprite file format for Creatures2 (The S16) files is not very complex. It consists of a file header, then sprite description blocks, and then sprite data
S16 File Header
LONG flags
WORD SpriteCount
The Flags field is a 32bit field in which the upper 31 bits are reserved and should be zero. The least significant bit indicates the file format of the file. If the bit is set, then the file is in 565 format, if clear, then the file is in 555 format. The Sprite count is the number of images in the file. If the count is non-zero, then the following sections exist
Sprite Headers
The Sprite Header section of the file is defined as follows
{
| LONG | Offset | The offset into the sprite file of the image data. |
| WORD | Width | The width of the sprite. |
| WORD | Height | The height of the sprite. |
}[SpriteCount]
Therefore, there are two words and one long per sprite in the file at this point
Sprite Data Section
In the sprite Data Section, the following is defined
{
| WORD [Widthn*Heightn] | Sprite Data | Each word is a single pixel. |
}