Well, I have a series of novels called the damnation chronicles. It's more dark fantasy than horror, but has some horror elements. It deals with hell, the apocalypse, and that kind of stuff. It would be better if you took a look at my site, www.josephsweet.co.nr i write it, but describing it I'm sometimes not so good at.
Not sure on budget at the moment, but I don't think it would be much. It would be better if you told me what you charge for between one and five illustrations.