Hmm ok I'll try. I'm definitly not an expert and this is just my opinion. I'd say it is not a bad start but definitly not enough to make a VN or game. I'll go from image to image and try to explain what/how you can improve.
1st image: I like the lighting in this on. Some nice shadows.
You see those black lines on her forehead? These are caused by the hair. The hair cap is clipping through the model, which you can also see when you switch to "smooth shaded". That's why every hair has corrective morphs to adjust it and get rid of those. Just select the hair and go to parameters.
The pose looks very unnatrual. I have never seen someone sitting like this. Try to imitate the pose you want to create yourself and look how your arms and legs behave, what parts touch the ground/bed or whatever.
The background is too empty for my taste, especially with the palm hidden. The HDRI is blurred but the rest is sharp which is confusing. Either you blurr them all or hide the HDRI (changing the camera angle, so it isn't rendered).
2nd image: Again I like the lighting.
And again there are the black lines from the hair. And again the pose looks unnatural. She is lying on her arm, her boob and her leg... Her right foot and her ass are flying in the air and her left leg is clipping in the right. Why is there the stool in the bottom right corner, if it isn't used? It just irritates the viewer and changes the focus. And again I don't like the blurred HDRI while the rest is sharp.
3rd image: This time I like the pose. It looks much better, more natural to me. The lighting is not bad too. Even though I don't like when the light comes from the front. This way you wash out all the shadows. Out of all images, I like this the most.
Again the black lines from the hair. The clothing on the ground, is not on the ground, it is flying. So yeah, I'd use dforce clothing for this. Otherwise there are some "messy clothing props" out there which you can use too.
4th image: Sorry but I don't like this one at all.
The lighting is way, WAY too bright. Can you see the white areas on her skin? That's the light literally burning out all the details. No shadows, nothing. Just way too overexposed. Again the pose looks weird and unnatural, especially the right arm. Again the background/the room looks pretty empty.
Some general tips:
- the typical resolution for a game is 16:9 HD (1920:1080), yours is 1000ish:873
- try to get rid of noise, either you use a denoiser or you let them bake longer (for a scene I'd say at least 1000-5000 iterations)
- use dof (depth of field) to focus the right object/character, everything out of focus gets blurred
- I said I don't like the blurred HDRIs, on polyhaven(.com) you can find high-quality HDRIs for free
- Lighting makes or breakes an image (as you can see in the 4th). My way to go is 3-point-lighting. I mostly get pretty decent results. When you are getting better and more confident try to change color and temperatur of the light source and maybe imitate real light source like sun, lamps,...
- literally every technique used in photography (like 3-point-lighting) is useful for 3D-art
- like I already said to posing, try to imitate the pose you want create and check for clipping and poking through clothes, useful tools for this is the smoothing modifier
I hope I wasn't too harsh and could help you a little bit.
