All details, eh? Well, I guess you could make it rather big (not gigantic! XD) with one side be a greyish dead field with Darkrai on it, and the other side a lush forest with Celebi on that side. By the Way, put Celebi on the RIGHT side. (Your left, I guess.) In the middle, make it say:
Time and Darkness...
Two great forces...
Who will prevail?
Find out in Pokemon! Mystic Dreams!