sauvignon1: It's an iconic album cover.
But the story behind it would be the story of why you like Court of the Crimson King so much?
For me it (the album, not my avatar) is an album which was put on tape for me by my brother-in-law, who liked King Crimson a lot. I recognised "I talk to the wind" from a seventies-psychedelic tape someone had put together for me years ago and when I heard the whole album on the firstmentioned tape, I decided I liked it so much I bought it. It got company on my CD-shelf by Circus, Discipline and Three of a Perfect pair later on.
A completely different story, that of my avatar: For my first Baldur's Gate character I unknowingly picked Xan's portrait, only to find out later it was an NPC's portrait I picked. My second runthrough of Baldur's Gate I created a half-elven bard and liked to give him a similar portrait, as I'd fallen in love with the look of pointy ears and purple robe. So I went scouting on portrait sizes and found this portrait for my bard named Kheltick. When I got to know GOG, I wanted an avatar that had to do with what I think is the Goodest Old Game (or more grammatically correct, the BOG - Best Old Game): Baldur's Gate. The choice was easily made, cropping the picture to make it look right this small took some more time (I wanted the face to be still recognizable and thus compromised robe and ears).
If you think TL;DR, well, the question was for a
story, right?