Link to the original Aikido Journal page featuring the photo of Ueshiba: http://blog.aikidojournal.com/2011/1...tanley-pranin/
(as Peter stated, the setting is the new hombu dojo, and was taken the year after the dojo opened).
I'll set the table for Hunter by posting a pic of Minoru Akuzawa, who also rarely is photographed in bare feet it seems.
Rob John has mentioned that Ark has developed the traits Hunter pointed out regarding the feet. Dan Harden has stated that the wrists and ankles tend to thicken over time when following Dan's training methodology.