Well, there are other tartans out there that you might choose to wear that you can assign some religious signifigance to, without implying that you are clergy.

Get creative. There is the MacIntyre tartan (MacIntyre means "son of the carpenter.") There is the Shepherd tartan (you can tell people that your chief is the Good Shepherd). But the problem with this approach is that while these tartans may have spiritual signifigance to you, other people will see them and just assume that you are a MacIntyre or a Shepherd.

The Clergy tartan has obvious religious signifigance, yes. But the problem stands that it implies that you are a clergyman. Sounds like what you are looking for is something that implys you are a Christian. Some have likened wearing a tartan to wearing a Notre Dame sweatshirt. People see you wearing it and assume you have some connection to Notre Dame. But the Clergy tartan is more specific. It doesn't just denote allegiance to a clan or place. It denotes an occupation -- an occupation that most people hold in very high regard. So it wouldn't be quite like wearing a Notre Dame sweatshirt (I'm a fan of Notre Dame), as it would be like wearing a name tag that said "I'm on the Notre Dame faculty."

The fact is that there is no "Christian" tartan. No tartan that simply says, "I'm a man of faith." (Think about it -- in the past, it likely was not an issue. When 99% of the population in your area was Christian, why would anyone need a special tartan to point that out? We obviously live in different times now). So one option woudl be for you to design one. Obviously, given the intent of the tartan, this would have to be done with great taste.

Understand this could not be an official tartan -- it would only be a fashion tartan. You'd never get the approval of the clan cheif! It would likely be recorded as "a tartan woven for X to denote his Christian faith."

Why not begin with the Clergy tartan, and alter it slightly. Keep it similar enough that people would still be able to recongize the Clergy tartan in it, but different enough that people would notice the difference.

If you want to go that route, I'd be happy to work up some designs for you. Just PM me.

Thanks!
Matt