It isn't a pattern realy... I'll try illustrate with letters...
B=Black
G=Grey
X=LightGrey
Top graphic (7px high, 1px wide):
G
B
B
B
B
G
X
TopLeft(7px by 7px):
GGGGGGG
GBBBBBB
GBBBBBB
GBBBBBB
GBBBBBB
GBBBGGG
GBBBGXX
GBBBGX
Well you see the pattern, no use in going on
Regards,
Andraax