It's great that you're open to feedback! You're doing great!
I've done a drawover, mostly as a thing to learn from for future pieces. I've tried to keep your proportions largely intact so it still feels like your style and keeps those elegant, long proportions.
I think trying to exaggerate the cards, even if it makes them bigger than is necessarily realistic for a playing card, might really help them stand out on the cover. I also threw a little shower of cards across the figures to scream "THIS IS ABOUT CARDS!" because Tapas covers are small and it being a GL about cards is kind of the unique selling point.
Watch the middle point of your faces. While it's fine in a manga style to play a bit fast and loose with this, particularly since the eyes are bigger, try to watch for things like making sure a parting in the hair is above the nose in perspective, and that eyes still feel like they're on the front of the face. The further eye on the Brunette is maybe creeping off a bit too far around the side of the face there.
The chest on the blonde is one of the biggest changes, because when the back is arched like that, and the neck pulled back, the chest would thrust out, and due to the curvature, the boobs would be higher up. I admit, I'm not the most amazing at drawing big boobs myself, so I've kept things pretty vague there
Also on the other lady, I've had the tie get pushed out by the chest to really emphasise the sense of there being volume there.
The stuff about the....er.... groin topography only applies if the character is a cis woman or is post-op if trans, obviously. If you have that area with a line as you have it right now, it looks like she has a bulge that protrudes out and below the leg joint, which could be intentional, so feel free to ignore that part of the draw-over.
Anyway, I hope that's helpful. Boomer's advice to pick a light direction is also a very good idea. A more consistent light direction, rather than both figures being shadowed on their further side, would probably add a tough of extra polish.
Whatever you decide to do, good luck! 