Is it appropriate to serve chilled white wine on a winter's afternoon?
Yes - if you think that that is what your guests will enjoy.
Impossible to answer without context. Serve where? to whom? why are they there? It would be inappropriate to serve it to children, or a room full of recovering alcoholics, Mormons or Baptists, etc. You see where this is going?
Of course. People drink cold drinks of all kinds all through winter. If people are having seafood with wine - which they often do in winter - they are almost likely going to have it with white wine and the wine will not be cold. Restaurants serve white wine all through the year and it is commonly served chilled.
Now if you are asking if chilled white wine should be the only choice (assuming this isn't a meal in which chilled white wine would be the appropriate choice) for a winter party, the answer is probably no. For instance, many people will not want to drink something cold at a winter cocktail party.