Attractive commercially produced curtain finials seem to be a hard thing to come by. They are either cheap and plastic or way to over the top to appeal to my taste.
I had this idea after having curtain rods with hollow unfinished ends for a while. There are a lot of really nice cupboard/drawer pulls and knobs around at the moment. I purchased these beautiful ones from Afez of the Heart in Bunbury but they are readily available both online or in local homewares stores, I know Tatu Homewares in Dunsborough has a bit of a selection. I just push to screw in part of the cupboard pull into a wine cork and inserted the cork into the hollow ends of my curtain rods.
I like them because they are a bit different and add a bit of colour and style without being overly fussy.