WOTC Miniature 
The Official Site reported [28 July 2005] the forthcoming release of an AT-AT walker in the 34mm miniatures series by Wizards of the Coast. Miniatures in the 34mm have a scale of approximately 1:47.4 (estimated by interpolating the scales of other miniature standards, tabulated on web pages). The true height of an AT-AT walker (in the movies) is approximately 22.5m, which would imply a miniature 18.7" tall. The erroneous height of 15m, published in old roleplaying sources (primarily West End Games') would imply a miniature 12.5" high. The reported height of Wizards' AT-AT toy is 16". This is too small (unless the walker is crouching) but is an improvement on the old WEG figure.
The reported length of 13" is more difficult to explain, since the canonical AT-AT walker's length is greater than its height. Perhaps this measurement excludes the head and neck?