The correct answer
is shown in the illustration.
No tile is
in line (either horizontally, vertically, or diagonally) with another
tile of the same design, and only three plain tiles are used. If after
placing the four lions you fall into the error of placing four other
tiles of another pattern, instead of only three, you will be left with
four places that must be occupied by plain tiles.
The secret consists
placing four of one kind and only three of each of the others.