Hm I don't want to lose the ability to have a detailed background since the visual quality is an important factor to our game and don't want to lose the stylistic coherence of our game so outlines would sort of stand out in a bad way. I think I'll try to increase the value difference between the platforms and the background by making the platforms brighter. Maybe I'll also increase the saturation of the blue lines on the platform. Might work...
Either way, thanks again for your insightful feedback.