A way the graphics could be improved would be to rethink the utilization of the color palette, while black and red are two good colors to mix together, it felt like there was little to no contrast nor balance between both. One simple way to balance both colors would be to use one of them for the platforms and obstacles, while the other is used for the characters. That way it would be easier to differentiate elements in the game; however, this is just an example, not a rule. There might be other ways to improve the graphics aside from the example presented in this reply, and I would admit that I respect and encourage your choice of trying to recreate a unique experience.