Comment 1 for bug 285597

It's extremely simple to have a background color preview in the icon view using a layer.
Just create a layer and send it to the back, and create a square of the size of the icon area. That way you can preview any background color you want and you just have to toggle off the visibility of that layer (or just remove it) when you're done.
I don't think it is worth to add an extra feature. It's something easily achievable with the current tools and it doesn't require a lot of steps.