If you haven't tried drawing your own graphics for your games, it's probably because you think it's too darn hard, but trust me when I say this: It's not. Drawing entities is one of my favorite aspects of game design, and I'm gonna show you how I go about doing it by presenting a few examples and showing you their progress flow.
Here's two entities I drew tonight, Grass Snake and Tentacle Bean:


Both entities start off as very basic shapes and hardly resemble their finished forms. The first thing to do is to get to work fixing up the lines a bit, making them less blotchy. This is the part that takes allot of time, but don't rush it, just keep fixing the lines pixel by pixel until you're decently happy with your entity's overall shape. Once it's the way you want it you can start on the coloring. Decide what midtones you'll be using and establish both darker and lighter tones of them. The darker tones are used for any area of the entity that has a shadow cast upon it or is shielded from light, and the light tones are used to provide a shiny, metallic or reflective look to objects. The mid and dark tones are used much more often than the light tones, and sometimes you won't even need the light tones at all.
Creating a humanoid template is very beneficial, as it'll open the doors to all kinds of enemies for your games. As always, start with simple shapes and just alter the sizes of them until you've got a rough template, then it's just a matter of recoloring clothes and adding extra features to create any humanoid race/class you want:

Anyways, good luck, and I hope to see some awesome home brewed entities in up coming games!
