If there is a cross it should be discrete, nearly subliminal, as a hint of things to come.
Ooh, yes, this I like.
But yeah, in general I do think that the cross should be primarily emphasized in the Lent-Holy Week-Easter sequence, whereas the Advent-Christmas-Epiphany sequence should make use of other central symbols--the star, perhaps, although the relevance of that only really comes in towards the end, or the creche, although that can get real kitsch real easy. Perhaps there's not as immediately obvious a possibility as I went into this post thinking. Pentecost of course has the tongues of flame, and those are hardcore.