Peace,
Christians don't actually venerate the images of Mary, etc.
We see a picture of Mary or Jesus and it reminds us of them, so they are often on our minds. We're less likely to sin if we're thinking about Jesus and Mary.
And that's just my take on it.
And the crucufix reminds us of Jesus Christ's passion, death, and ressurection. It's a commemoration, if I may put it. There are commemorations for World Wars and 9-11/