You have all the time to rearrange or polish your flower arrangement. The flower design should look beautiful and artistic enough before you place your filler, when the filler is already placed, it would be harder to move your things around the area or place. Bear in mind that The filler are very fragile.
Feather flowers are going to be the stars of 2013. There are some amazing designs out there already that include organza or silk with Swarovski detailing and a feature vintage Marcasite or crystal brooch. Look out for the Coq feathers!