Don't mean to be too obvious or trite, but
Holly and
Ivy are nice ones for Christmastime. Of course, there's also
Noel or
Noelle. For
Easter, if you recognize it as a religious event, you might want to try a name that ties in with the atonement, death or resurrection of
Christ: Names like
Grace, or Ransom (usually for a boy) might work. If you're willing to use names from other languages, there's
Salvador or
Salvatore, meaning "savior." I'm sure there's a host of others you could find among biblical names, such as
Isaiah,
Joel,
Elijah, and so forth.