/3/ - 3DCG

>>683155
If you add a very very fine noise mostly on the background it will get rid of the color banding.
You should be able to set up your renderer to mask out your character when doing this, or just bring the image into photoshop. Essentially it works like pic related creating a dithering effect that blends your gradient. If its too noisy at the point where you feel it blends the best add a very very light Gaussian blur. Also make sure you're working with 16 bit color depth on your exported images.