Apart from round the sheltered bits of Stornoway, trees are rare in the Outer Hebrides, though there is much planting afoot which will change this over the coming decades. When wandering around, you'll occasionally see a Rowan tree. For centuries this was believed to protect the household, cattle and croft from witches and fairies and is present to this day on many crofts near the house. There was great fear about cutting down a Rowan: this belief can be traced back from the Celts to the druids.
Below is another cracking picture from Bluewave; this one of the tree at Ach Mor on Lewis.
This tree, which sits on its own, apparently has a number of stories surrounding it. It probably has several names in Gaelic, one of which I've been told by a local translates roughly as "The tree of knowledge" - why, I don't know but it's a safe bet there's a story or legend behind it. The slant of the tree is testament to the gales and occasional hurricane that blow through.
Judging from the number of comments, the picture is a popular one on Flickr; the original large size makes for an excellent screen background.
Here's one from Niall Corbet of someone windsurfing, or powergliding, or whatever this variation is called, off a beach of Barra: