This is slightly overlevelled/burned so you can see that there is a loss of anti-aliasing detail throughout the entire page. Kain's left elbow in panel 1 is missing some white detail. The greys are pretty nicely done for the most part except for the ceiling in the big panel and the girl's eye in the final panel. Loss of detail is the main thing here - there are two shades of grey in the ceiling and her eye is more complex than black and grey.
Psychobob's dots and screens packs have more than enough patterns to support two tones of grey. As for her eye, I would have just left it as is without cleaning.
Overall a good effort. I hope you continue attempting future challenges to improve your skills.
to see how to make the gray fade away (floor):
after doing the the gray layer, create a new layer over it.. put some white (with the brush) at where it should be white (duh) thus at the end.. then lower the opacity of that layer. then take the smudge tool, and smudge the white toward the gray part (always on the white layer of course).. to make it uniforme, smudge the white that's in the gray part from right to left with lower strength (like 20% or so)