I've had a complex relationship with illustration. In school it often seemed to be something that should never mix with graphic design. My zine had "too many" of them and therefore I should be looking into switching majors. Alternately, it's said to be impossible to achieve for graphic designers; they simply "can't draw." Now that I'm a professional designer, however, I find it's actually been incredibly helpful to be able to draw on some level, especially when the client can't afford a full blown professional illustrator and graphic designer.
Case in point: an infant clothing start-up that was supposed to benefit endangered species approached me to illustrate a sea turtle, polar bear, and tiger. Here are a couple full sets I submitted:
Do you have any favorites? Let me know what you think!