This image is of a 12th century mosaic, depicting St Andrew, in the Basilica San Giusto Trieste.
St Andrew was an apostle of Jesus and, among various other things, he is the patron saint of Scotland, among other countries like Barbados, Romania, Russia, and Ukraine. We’re going out tonight but will be celebrating tomorrow with haggis, neeps, tatties and cranachan (at my insistence – I spent nearly seven years in Glasgow for those of you who don’t know!) Different traditions exist around St Andrew – he probably never actually went to Scotland, and it states in the Old Testament that he was the brother of Simon Peter. Both were fishermen originally – although as with many things, it depends a bit on which Gospel account you read. He was apparently (according to later tradition) martyred on a X-shaped cross, hence the Saltire still being the flag of Scotland today. He is even mentioned in the Declaration of Arbroath!
St Andrew’s Day is celebrated across the world, although I’m obviously most familiar with the celebrations in Scotland – I’m basically just using it as an excuse to have Irn Bru and cranachan! Neither of those are things which St Andrew would have had (although if anyone has evidence to the contrary, reports of him knocking back the whisky would be hilarious!)
Apparently, St Andrews Eve also marked the start of ‘vampire season’ – this (according to Wikipedia, so it is perhaps best taken with a pinch of salt!) last until the night before St George’s Day. There’s lots of legends regarding St Andrew and young women invoking him to find husbands, and apparently there was a connection between Andrew and witches.
There is a bit more information about St Andrew here, for anyone interested: http://www.bbc.co.uk/religion/religions/christianity/saints/andrew.shtml