Art is important to the whole of your product. It shows the customer the length and time you are willing to put into your product. We, at
Alea Publishing Group, when forming our first product, wanted our product to look clean, professional, and comparable on all levels with WOTC products. We took extra care in our page layout and with the artwork we used and created, especially the maps for our products.
Our customers as well as those we have talked with passing our tables at cons have remarked on the professional quality of our product. It also sets you apart from other publishers (especially in the .pdf market where third party products abound).
Also, I have met a lot of GMs (I am one of them) that are hesitant to use non WOTC products (our products are an exception). Artwork helps you bridge that gap as a professional and draws those skeptics in to read the rules you have worked hard to produce.
Our free product
A Question of Honor: A Game Enhancement is an example, from what we have found, to be a good example of this.
I must say, however, Monte Cook has done well with minimum artwork, however he is selling his name and reputation as a game designer (I must also say, though I respect Monte Cook, I did not buy Arcana Unearthed for the fact that it had a bare minimum of artwork).
Anyway, I think a well designed .pdf puts skeptics at ease, not only by looking professional as a quality product, but as a great alternative to a print product.
Joshua Raynack
Alea Publishing Group