The Flood Gallery in Greenwhich had an exhibit last week commemorating the 40th anniversary of Led Zeppelin IV. The exhibit featured eight different pictures, created specially for the exhibit, each commemorating one song on Led Zeppelin IV. The Black Dog and Stairway to Heaven posters are also available in different colour patterning. As well, there is an exhibition poster, plus a poster depicting the entire set.
In total there are 15 posters ranging in price from £20 to £500. Personally, I ordered the exhibition poster.
Posters can be seen, and ordered from the Flood Gallery website.
Dave Lewis was, of course, there and has more.