Well, I find myself in the minority here, but I for one think tartan ties are fine with kilts, as long as general rules of fashion are followed.

For example, if you are wearing a tie in the same tartan as your kilt, please make sure it comes from the same manufacturer, so that the colors will be a true match. Nothing looks worse than wearing a kilt and tie in the same tartan that you purchased from two seperate places in off-colors.

I even think that, sometimes, it can look fine to wear a different tartan in your tie (gasp!). Although I think this is helped by wearing a vest or sweater -- something in a solid color to separate the two tartans. And, of course, make sure that the two tartans are complimentary, both with each other and the rest of the outfit.

Of course, I don't give this out as general advise. If you don't have an eye for matchign different patterns, a solid color tie is really the best way to go. But I'm just saying I have seen it done, and done it myself (hopefully), where it looked just fine.

Matt