Often the background colour is easy, sometimes there are several that have potential. Eventually I just feel more comfortable with one colour and the others go. (I used to do the same thing when I was working on a quilt design. Lay all the fabrics on the loungeroom floor, move around and past them for several days and gradually some would have to go, others would leap out and take pride of place, sometimes even changing the whole colour flow taking me back to the start.)
With this portrait, the background was very tricky. I wanted to use a silvery paper which blended really well with the work, but my husband felt the purple made the colouring and her facial features really stand out.
As you can see the purple won!
Mum and dad are very keen gardeners, not often dressed up, so I put little rhinestones on each earring to add to her gorgeousness! 20 different coloured papers, 8 layers.