So I guess you know this since you drew it, but the relation between the length of the upper and lower body is 3:4. I remember that when I first looked into manga I saw some tutorials that encouraged those proportions, but I have still never actually seen someone use this in a reasonable way. One of the problems that emerge when the upper body is too short is that the arms either needs to be adjusted to fit the short upper body (so that the elbows line up with the lower part of the ribcage), or they are kept at the correct length in relation to the legs. In the first case the arms will seem too short, and in the second case the arms will seem too long. If you want too avoid making this decision I suggest you keep the ration approximately between 7:8 and 8:7.

Yeah but good job, and I just want to point out that even though this is Manga Tutorials a lot of the artists around here are very good at art in general, and if you want feedback on a piece that isn't really manga no one will rage on you for posting it here.