The reason there are no real Walker tartans is because of the heritage of the name. The Walkers were not from the Highlands. For example, my own branch is from Newcastle. Associated with the weaving trade, there are two stories, one being that the walkers were the ones who "walked" the fullers earth into the fabrics as a part of compressing the wool fibers. Another states that they were the ones who walked the length of the looms attending to the bobbins. When the Walkers used tartans later, the patterns were those of allied clans. The Tennessee tartan is no more the official Walker Tartan than would be a coat of arms that anyone would design for their own family unit. I did find it interesting that there appears to be another Walker on the forum with a coat of arms that is almost identical to the one used by my family since the 1600's.
Clarence W. Walker (Family arrived in Mass and then, like, many Scots/Irish, followed the Herkimer Valley into NY State at the beginning of the 1700's)