I understand where Frog, and MB1 are coming from when they feel there should be some sort of fixed object to focus on, but in this particuliar image, I feel, there is enough color, swirls and natural patterns in the clouds (and softened with a long exposure) to make this work quite well as it is. It looks like a piece of contemporary abstract art that i could see framed and hanging in someones modern decorum. I would suggest a very slight increase in contrast with either a leyer or curves adjustment. I think the swirling patterns and colors are very good here.