Randy is correct; the site needs more keyword-rich text. But since you find yourself in the "unique" position(

) of having a website owner that is obstinate on their design, you can still plant your keywords in the page title and keyword meta tags.
Also the <img> "alt" tags are another source for keyword placement since there are so many graphics. Whatever you do, don't go "black hat" and hide keywords behind the graphics or by using the same color text as the background or the site may get banned from the serps.
Checking the keyword combinations you've come up with, there's no reason you shouldn't get top ten placement in Google (and others) for the organic search results with these keywords (especially if you get the site owner to change their mind and add some text).
However, may I suggest going with these keyword combos - "custom sign", "business sign" and "sign shop". If the owner of this sign business makes neon signs I'd go with "neon sign" as well.
According to the Overture Keyword Suggestion tool -
"custom sign" had 8599 searches, "business sign" had 5831 searches, "sign shop" had 3489 searches and "neon sign" had 22066 searches in January '07. "virginia sign" had 200 searches and 'west virginia sign" had 183 searches for the same period. Not great for keywords.