When is a painting done?

I have had the painting from the Saturday workshop out in my house, leaning on a wall, and I have spent the past few days living with it. I do not think it is finished! Sometimes when I do a demo my paintings are challenging, especially if I don't capture a flow in my 2nd and 3rd layer of washes. I look at this painting and it just doesn't feel right to me. 

I have not had time to focus on what is missing but I do know I am happy with the composition. Ever since I have been playing with collages in my artist trading cards I keep thinking about how the cards can be used as a small study that can lead to a bigger art work so I am planning on adding collage elements to this painting. I want to add some fun - maybe gold glitter, yarn, even my ink stamps of ferns in the foreground. I have been adding embellishments to my art cards and just yesterday at the reception I went to I met a jewelry artist who suggested I use copper wire to wrap around embellishments that can then be collaged into my artwork. All these new ideas keep my mind busy and I am still working through what changes I want to do with the watercolor from Saturday but I definitely see collages in my future.