I just would like background ideas that are going to highlight this peice

My partner loves a Porsche 911, this model in particular. I’m making this peice for his birthday. I’m tracing the cars (don’t judge I’m far out of practice for freehanding this lol) and I am using a water color/ acrylic mixed medium. On to the question at hand: What would the best cohesive background be to highlight all four cars?

Note: The car itself will be almost vibrant lavender color