Now that the extended fight with activist investor Dan Loeb is finally over, Sothebys (NYSE:BID) can finally turn its full attention back to running auctions, and based on recent sales of contemporary art at both Sothebys and Christie Group plc (LON:CTG), there is a lot of room for growth. Impressionism of growing importance, Christie’s auction sets a new record While Sothebys (NYSE:BID) recent sale of impressionist paintings was a bit disappointing, its contemporary sale brought in $364 million against an estimated range of $337 million to $474 million, with 85% sell through and more than half of the paintings selling…