I have had a book ( 'Mythic Ireland' by Michael Dames) sitting on my desk for some weeks now, and only just have I *looked* at the cover. It is a picture of The Great Yew in Crom Castle, but what makes it unusual is that the picture is upside down, it's gnarled mass of branches looking like exposed roots and the mound around it's base looking like the tree top.
There iseems to be no mention of why this imagery was used, but it is a really powerful one.