Images 1&2 by Caroline Andrieu. Really nice shading and I love the natural lines. Wish I could get it perfect like this.

Image 3 by Cedric Rivrain. Very strong use of lines and the bold colours in this particular illustration work great. Very edgy style.

Image 4 by Hanna Muller. Very cute designs and all illustrations seem to play by this rule. 

All illustrations are very similar with their own distinguishing mark. This is the style I love and I take inspiration from these artists all the time.