Infelizmente, não acho que seja possível.
De acordo com as respostas.microsoft.com:
I believe in the Final Release you cant change the size of the tile. Usually you can right click a tile and if you can change the size it will tell you at the bottom of the Start screen. I also tried moving it to a new column by itself and it still stayed the same size. So to answer your question I don't think there is a way to change the size of the Internet Explorer tile
Redimensionando o Mosaico do Internet Explorer 10 na tela Metro
Desculpe, cara.