I agree with you to the extent that faith should never be made a commodity nor materialized (which is why I'm not a fan of wearing cross necklaces--I like to think that I wear that cross inside). But I think that you go too far in saying that I "advertise" Christianity by making a link between Jesus and a vertical stabilizer.
I don't see this shirt as some ad for a religion, but a statement about the nature of Christ that is worth some consideration, if not deep analysis. I don't expect anyone to go to church for the first time in their lives because they see this shirt. (If that were the case, I would wonder how much faith and understanding they really had.)
As for your statement that my faith is supposed to be "between me and God:" well, you're right. That's whom I have faith in. But if religion were ONLY between God and I, I would never donate money to a charity. I would never have the chance to talk about God with other people. I would never be inspired to serve at soup kitchens or go to anti-genocide protests. If it weren't for me applying faith in public life, I never would have done any of these things--or make a dorky T-shirt.
You have the right to rebuke me if I am ever ostentatious due to my religion, just like Jesus took offense with those praying in public.I hope that you will. But if Christianity for me were reduced to a relationship between God and I, I would have much less of a chance to do good in this world.
Hope this cleared a few things up.