Panda...
Don't just darken the background with black...
Other options include: (1)reducing Hue otherwise called Desaturating. This means you take away color. The caveman version of this is adding grey, but go for a greyish blue or whatever type of color you want.
(2)Cooling off the background with blue or violet go for very grey blues or violets. You could also try other hues/colors, those just come to mind.
Your colors are very saturated, any desaturation will create great contrast and depth.
Don't just darken the background with black...
Other options include: (1)reducing Hue otherwise called Desaturating. This means you take away color. The caveman version of this is adding grey, but go for a greyish blue or whatever type of color you want.
(2)Cooling off the background with blue or violet go for very grey blues or violets. You could also try other hues/colors, those just come to mind.
Your colors are very saturated, any desaturation will create great contrast and depth.