Hm. Actually... Stick a moderately faint logo/rose thing in the moon behind them? The "Mysterious Symbol" might indicate that there's a plot line that's at least as important as the relationship plot. Stick with the purples, make the rose/design a different color to stand out (despite being faint/having a high transparency), make the viewer wonder what the heck the design is all about -- and then draw them into the nuances with the blurb.

Or so I'd give a shot, anyway.