There is a painting that shows a 'peasant shoe' of straw, like the traditional German strohschuh.
Meister der Karlsruher Passion, Kreuztragung Christi
1450Colour version here
, and large bildindex version here
. See the guy in the lower right-hand corner? It does look like he's wearing shoes made from plant matter. I can see this being another way of making an overshoe to protect any nicer shoes. (It seems to be assumed though that the straw shoes are the only shoes you own. At least he's wearing hose between the straw and his bare feet.)
Did I mention that the man also has a really sexy-looking wooden bucket?Edit:
Trying to find a clear photo of the 'patten' worn by one of the statues of the Fontana Maggiore
hasn't yielded anything yet. Edit, again:
Some 12th century sculptures:
Madonna by Benedetto Antelami
, Morgan Madonna
from Auvergne, Virgin and Child
from Morez, lots of 12th century-related pictures
Managed to find the stained glass windows
from Elisabethkirche zu Marburg (before 1250). (Middle of the second row.)
There is the possible pattens being worn by the Apostle Bartholomew
Full pane: http://www.elisabethkirche-mr.de/rundgang/fum_btr301.htm
I'd consider these to be pattens rather than sandals, because John the Baptist is in the pane next to him, and they took the time to paint his bare feet.
However, these are rather plain shoes, especially when comparing them to Marys' decorated shoes (from the second row, first on the left.)
Full pane: http://www.elisabethkirche-mr.de/rundgang/ful_btl101.htm
Or Elisabeth http://www.elisabethkirche-mr.de/rundgang/ful_btl201.htm
There is a bishop, also with decorated feet but he's 14th century.