If this business, ninjacore, is not for an artist (where one can apply different standards), I don't think a dark background is appropriate.

However one of my clients had a lovely dark picture she wanted to use on her business website as a background, and the way I was able to accommodate her request was to lower the opacity of the image until one could read the text normally. [transientspecialists.com]See for yourself.
An alternative would be to set the text color to white (css
color: #ffffff;) or some other very light color, but you have to determine if the text can still be read easily. And if you go that rout, don't forget to change the color to black on your printer friendly version of the page where,
in any case, the background image should be removed as a courtesy to the site's readers.
Hope this helps.