I think it's always been pretty obvious from the beginning that Fai knew something (actually, a lot of things) he wasn't telling. Between the happy act he'll show a heck of a lot of insight when it's needed and surprise the rest of the group. And especially concerning magic, he picks up on a lot of things, and sometimes the manga makes it clear.. like the castle in Koryo and in Lecourt, and sometimes it doesn't. Like remember just *who* it was who found the first feather buried *inside* Syaoran's cape where it wasn't even visible. I think there are quite a few little hints of Fai's magic like this... and I still wonder why Fai was so eager to stay behind in that bunny world. Suspicious.. ^^;; Although I find it amusing that with all his magical sensing powers, the person that Fai looked at first after he'd transported to Yuuko's world was Kurogane. ^___^ Love at first sight, I tell you.
Oh, and to keep this topic from cluttering more than it already is, please post pictures in the fanart section or in the colored manga thread here in the manga section, and people can comment on them there. Thanks.