Anotomy lessons are your friends. Those might be alright, but they aren't the best, and they aren't all that great overall. A breast larger than it's fellow, and overly large at that- do you know how cliche and over used SUPER LARGE BOOBS are? :/ very. There's also other errors like the second's pic face looks .. smashed and triangular, the eyes are askew. For the second pic, outside of the eyes also being .. off, and the breasts different sizes, the hand looks like a foot, to be honest.
So yeah. Keep practicing. Oh and the leg of the second pic also looks off. Mostly because her thigh goes from being FAT to STICK or something along the lines. Just, as I said. Anotomy. Use it. It keeps your people from looking wtf, makes them more realistic.