I suppose there is nothing wrong with seeing God in unintended symbols such as a sign on the side of a bus. We often see God in sights in nature such as a beautiful mountain view or while looking up at the stars. We can even see God in man made structures such as in a cathedral or a piece of art.
The one place where we should see God and often don't is in each other. I'm not saying in anyway that we are God. But we are made in the image and likeness of God. We should see each others as brothers and sisters. We should see Jesus in the face of everyone. I realize I need to work on this because, well lets face it, people are stupid. People are annoying. It is difficult to see Jesus in that person from work who talks too much and is always gossiping. It's difficult to see Jesus in the cubical next to you who has a body odor problem. It's really difficult to see Jesus in the people that I deal with at work. It may be the crack addict who has been "robbed" once again or the drunk who has passed out in the middle of the road and soiled himself.
Jesus tells us that the two most important commandments is to love God above all others and to love others as we love ourselves. I think that's why the cross is a brilliant icon for the Christian faith. Yes, like the vertical beam of the cross, we are to love and praise God. But we also have the horizontal beam of the cross. Like that beam, our love is to go horizontal too. Our love is to go up to God and out to our neighbors.
If I can see an image of God in a bus sign, why is it difficult to see an image of God in the people who are riding that bus??