Just a few more words …
I have no axe to grind but I have found,
Goodprint useful for producing business cards.
Shutterstock useful for purchasing clipart
FotoFlexer useful as a (free) on-line photo or image editor.
Converting a clipart image is not a bad way to produce a book cover, text is not too difficult to manipulate in FotoFlexer but fonts are a bit limited. You can drop an image into say the CP cover creator but their designs seem a bit cheesy to me. Using the full image gives a proper ‘book-like’ appearance, but the issue than is laying down the text.
I should add that there are quite a few on-line image editors so its a case of trial and error.