It's a nice idea for a site, and I think the white text on the black background is fine. Things I would change:
Get a sans-serif font for text that you have to read (names and phone numbers look good in the font that you're using but on the index page I would change it to some sans-serif font type and also maybe increase your line spacing to 1.2em or something, just to make it easy to read).
For an artsy photography site I would try my hardest to get the index page to show up without scrolling, you've got a lot of room up top and you can always make the main flower image a little smaller.
The link hover's drive me absolutely crazy because they make everything move. If you can't figure out how to get your line to extend all the way out without pushing everything else down, then just make a simple color change or underline when hovering.
These are all very minor aesthetic things. Other than that, the design is good, very simple and straighforward.
Might I actually suggest using lightbox to show large size images of the thumbnails, I think it would look really great.