The cel is not from his normal attack (the arrow 
is on the opposite side of the bow and his right 
leg is slightly different from the 'standard' 
attack) Your cel seems to be form the very 
beginning of the episode "Lady Kayura and the 
Dark Relm". It's used there for sure but I'm not 
sure if that is the sequence used after that 
point in the series (it's not used latter in the 
episode). I wish I had the ability to make a 
screen capture because the background used is a 
very cool picture of the earth. (I'm still 
jealous ^_~`) I have a similar cel of Cye that is 
an attack cel but it's not used in the normal 
sequence. Here's a pic but I think you've already 
seen it.

-Snakeskii-