I honestly don't recommend illustrations in novel. The simple reason is that your writing should dictate the scene. If you are having too much trouble describing something, here's a few options:
1) You don't really have to describe characters in detail. You just need to mention one distinguishable feature about them. The reader can imagine the rest. This goes for certain ethnicity as well. For example, if you would like to mention that the person is Japanese, you can do so either with the choice of name or later insert something that hints to their heritage. A situation would be where the MC opens the wardrobe and looks wistfully at a kimono that belonged to her late mother.
Let's say you would like to describe an Indian. You could mention how the MC looks at another person, whose umber-colored skin hinted at a Southeast Asian origin. And no, that is not racist. I know. I'm an Indian and I did not find that offensive in the least.
2) When describing monsters, mention the most horrifying feature and then a few more hints. For example, the creature stood up on two legs, it's tail swishing behind it like a rattlesnake's warning. It's jaws opened and a long slithery long slowly creeped out, like it was an entity with its own mind.
3) Check on Google for names of things. Don't know what to call a part of a car? Just type in "parts of a car" and look up the result or type in something specific.
In the end, description is not all that matters. Your characters, story, and dialogue all play a vital role in creating a fantatic narrative.
