Yes, while it's not official Catholic liturgical practice, there's also nothing whatsoever to prevent or outlaw the practice of Advent Wreaths.  We've actually seen not a few of the best elements of Catholic Liturgy introduced this way by custom that was later embraced by the Church, where if there's a gap in some area (neither for nor against), sometimes people filled in those gaps.  As Pax said, Christmas trees and Nativity Sets within the sanctuary are not uncommon, and I doubt that the Church before Vatican II would have had any problem with those.

What is it with everyone using AI now to argue various theological points?  Use your brain.  It's not an innovation simply because it's not an official part of any Liturgy.  I've seen chapels that put relics, or different types of statues within the sanctuary, and then you can find American flags (something I don't like but which had been approved by US bishops), etc.  I'm sure that there have long been various types of other decorations, flowers, wreathes, garlands, poinsiettas, Christmas trees with lights, etc.  I see them today, and I'm sure they were out there long before Vatican II.  Can you find something official that says you can put poinsiettas on the altar?  I doubt it, but priests and chapels make a regular habit of it, and there's nothing that says you can't either.  So if you can put poinsiettas on the altar (or the ledge behind the altar), then you can put a wreath in the sanctuary also.  There's no official list of "things not to put in a Sanctuary".