I'm currently finishing up a small (9" x 12") study in preparation for a larger painting. In addition to finding all the right hues for the large piece, so that I'm making changes on a small scale instead of a larger scale, thus saving time and paint, I'm also looking for the best value scheme to support my focal point and express form.
Taking a photo of your work is often helpful as it lets you see the image smaller and with details compressed, which will allow you to see errors that weren't as obvious in person. Even better if you are able to flip the canvas to get a mirror image.
Another thing that I regularly do, especially toward the end of the painting process, is convert a photo of my work into black and white and analyze the values alone. When I'm working with students, this really helps them to see where changing values will increase the depth and sense of form in their work. Often there are settings right on your smart phone or tablet that will allow you to make a monochromatic image without having to use a photo editing program.
We are commonly so hung up on color that we lose sense of the underlying values. Notice when looking between the two images, above, that some of the intense colors in the feathers and costume look much darker than expected in the black and white version. This is because the colors are intense, which we commonly erroneously interpret as "bright" or light in value.
It is likely that I will add some lighter values to the feathers on the right hand side of the painting, but overall I like that the lightest values in the painting are exclusively on the areas of the model's hair and skin. This means she will not be lost in the sea of hues and feathers which surrounds her.
By the way... I've been obsessed with peacocks lately. I'm collecting peacock imagery over on my Tumblr, and likely will on my Pinterest as well. (Some are tucked away in the Art Deco board. I'm obsessed with Art Deco, too!)