About drawings, it’s valid what we have said in this post about getting together images. Try to not make them by yourself.
It’s a general rule for everything. It’s good you can create your own cover, but use good quality images, always, as the ones we’re offering you or from the websites we told you in the post on how to look for images.
It’s possible to think that making everything by yourself will give a special touch, especially if you created the book, the cover, the formatting and everything else.
For sure there will be among you some good drawers, or you have a friend of yours that is good in drawing. Still, a potential reader looking among the mass of thumbnails on a store will notice immediately if you have an amateur drawing.
So, what to do if you don’t want a photo but an illustration? Choose one among the ones we’re offering you, or go to iStock and the others. It’s very cheap, there are many good works and you will have a professional drawing.
Illustrations, especially, always come with a JPG and a Vector file, so you can modify them with some professional editor.
Here there are some examples that you can easily find on iStock.