3/4 rule - cut the part of the canvas that is "dedicated" to the background, it only distracts attantion from the portrait. make it so the portrait fills +- 3/4 of the whole canvas.

Hey there! Great work! It's only my opinion but I feel like you are taking a way too realistic approach, which leads to a lot of airbrushing and messy values. It's not necessarily a problem, but maybe you should take a little more abstract approach. Try to break down the reference into shapes, instead of airbrushing everything together. @Sinix has several videos tackling this kind of issue, I think you should check him out! :) I'd really like to see some original work from you :) I hope I could help! Keep up the great work! :)

Hey Nathan, like the others have said, this is fantastic work! You've definitely gotten the likeness. I believe that the fact that you've got things so close is what's making it so difficult to see what's off. On my initial review, it seemed that the eyes may be a little large and/or slightly out of position. Particularly her right eye (on the left side of the image) My second observation was that something may be off with the angle/position of the nose bridge where it meets the eyebrows. As I mentioned though, it's so close so I wanted to be sure. I quickly popped it into infinite painter on my phone to do some one to one comparisons. One of the things I love about digital is how easy it makes it to compare your pieces to the originals with layers. In the first image I did a rough trace of the original photograph and fit your painting inside the head. You pretty much nailed the proportions of the overall skull so well done! Some of the things that stand out are that there is indeed something off with the eyes (and the irises) and nose bridge. Additionally I realized that the tip of the nose was a little off as well. Other things that could possibly be the culprit for it looking off are that the shoulder is lower, and the space from the edge of the arm to the seem has been shrunk. That last possibly major contributor is that the hair doesn't quite go high enough. There are a few other minor areas such as her left brow, her neck and the shape of shirt above where the scarf overlaps. I made a quick, rather messy adjusted image with the liquify tool, and included some side by sides for comparison. I may have missed some things but hopefully this helps you to nail down what was "off" about it. I've recently been grinding out head studies and they can be a real pain to get "perfect." Probably because we see them so often that we're very attuned to noticing when something is not quite right. Once again though, awesome job I can't stress this enough. It may seem like I listed a lot, but for every one of those there were ten that you crushed! Keep up the great work!

It might be your own perception that you think something is off, but the likeness is spot on and the shadows of the face look well valued. The only thing I can think of is the coat is not as rendered as the photo, and also the photo has a dark gradient of the left edge.