This is a little tool for viewing all possible 4x4 fill patterns, after removing duplicates which are the same pattern inverted, translated, rotated, or flipped in xydiagonally. There are 65536 possible raw fill patterns (1 << 16), but only 433 unique patterns once 'equivalent' ones have been discarded.
To use a fill pattern that you like, prefix it with '0x' (it is a hexadecimal number) and pass it fillp():