Your renders are looking very good from a lighting perspective, which is a big step. I think the next thing you might focus on is fine-tuning your posing and composition.
The render two posts up -
- She'd be pretty uncomfortable, after a while, with her head hanging off into space like that.
- His right foot is hovering up off the floor. Essentially, in this pose, he's about to fall to his right.
- His left arm is in a very awkward-looking position. Almost looks like he's about to make a fist and sock her.
- Should probably use a bit of DOF so that the cushions in the background are a bit out of focus, the way the candles are in the subsequent render.
- Not sure what that "thing" is on the left side of the render - can't decide if it's the top view of a hanging lamp or a fireman's pole. Similarly, not sure what that is at the bottom left. I'd probably have hidden them just to avoid the "what is that" reaction.
In the render in the post just before this one:
- First, this is a pretty good render, all in all.
- Her head looks like it's hovering up off the pillow.
- It looks like his left shin is hovering up off the bed. It could be that he's up on his toe, but it'd probably look better if it was flat on the bed.
- His right hand isn't down on the heel of his hand.
- Her hair would probably be behind her shoulders. Certainly the right fringes of it wouldn't be hovering in the air.
If you wanted to get REALLY sophisticated, the figures should be sinking into the bed slightly. Doing that is tricky, of course, and depends on the construction of the bed. If the bed's mesh is too coarse, it can be hard to make it look good, but you can potentially use a deformer to create a "dent" in the bed. But even if the bed doesn't deform, having the body parts penetrate just ever so slightly into the bed can sometimes give you a slightly more realistic look.
Mind you, these are all nits - outside of the odd pose that the first guy is in, there's not much to quibble about.