For the ninja girl
-the neck seems to be dislocated this is because the face is too much to her left when she is already looking towards her right...try this, tilt your head to the right, you'll see that you chin touches your shoulder. Basically, the path of the head rotates 180degree from shoulder to shoulder.
-Also if you care for skinfolds, the arm resting on the floor should have the skin or atleast the "flab" of the arm spreading on the surface, that's a bit advanced but it's fun to do those types of details xD
For the Fran fanart, since you did it in a hurry, I'm assuming that what I'll see here are areas that you do more like a trend so this may be areas that you have to focus on to resolve the trend. Going from top to bottom
-The facial structure seems to lack foreshortening on the waning side if you know what I mean. That is, her left eye needs a little bit more foreshortening to look correct. his also occurs on the ninja girl above but it's more evident here.
-The jaw as well does not connect up to the ears even though it's a given that Fran is old enough. As a note, only kids and fat/chubby people don't have prominent defined jaws
-The neck muscles surrounding the throat needs a fix. A good rule to follow is that the line marking the throat begins at the corners of the jaws and sink down to unite with the collar bones near the central axis of the body (also the sternum, this is because the neck muscle originates from the anteriormost end of the sternum and inserts on to the jaw) TMI xD sorry, occupational hazard
-the shoulders do need to be a bit more stable in a sense that they are sharper to the ends. Note also that the colar bone ends nead the edge of the shoulder, try feeling you shoulders and you'll notice a lump there that you can trace to the collarbone
-the armpits because they are important for me xD, try drawing in the pectoral muscles, deltoids and biceps to figure out how to draw the armpits and the skin fold there.
-The chest lacks 3dimensionality, if you are aware of the 45 degree rule from the collar bone to locate the nipples, that is helpful to locating the location of the silly goose in general
-The arms look a bit flimsy, also the upper arm is a bit too long , it should end right under the breast or right beside the last rib. (I do not know if Fran's race follows a different proportions though, I'm viewing it from a human basis)
-The hands are too complicated to teach. What I can say is that you should try generalizing the hand as a paddle then try to place in the fingers.
-The lower end of the but shouldn't curve that deep into the thigh, it should just touch then follow the thigh unless of course, the thigh has high fat density
-The front side of the thigh has a weird sink in it, it should just curve straight down because at that angle, only the quardiceps would be visible on the front side.
If something is unclear, just say it and I'll try to redline it.