diamond geezer has a magnificent Flickr set showing the beautiful artwork along London Underground's Victoria Line. It's 40 years old today and still looks fresh as a daisy. The designs by Hans Unger, Tom Eckersley, Edward Bawden, Alan Fletcher and others (quite a line-up) are pretty eclectic, but still look like a coherent set.

As dg points out it takes dedication to spot them all. Nice work!