How would your husband react to multi-color earth-tone tiles? You'd need to be careful to avoid getting too oatmeal-matchy with the counters... include some dark browns, some greens, and a little gray... possibly vary the textures also...

There is a black glaze for earthenware called Albany Slip. The finish is a very faintly silvery-metallic sheen. I'm sure there are tiles out there that have this glaze or something similar.

How about some almost metallic shades--I don't mean shiny industrial metal, but bronze, copper tones, etc., sort of like what you see in pottery.
If you can't sell the mulit-color, how about many hues of one color?

I'm trying to make out the material of your countertops. Are they limestone?

You may not prefer a modern look but how about a modern take on a traditional look?

These copper tiles are great. They come in a variety of textures and are actually a sort of synthetic copper so they will not tarnish.

http://www.stainlessliving.com/tile_spec4.asp

Why not do a 3/4" mosaic tile in a beige/gold/brown mix such as this one:

http://www.glasstilestore.com/ProductDetails.asp?ProductCode=coffebean

How about a little less multi- http://flickr.com/photos/arthurscircus/2213589791/
like this photo?

Oooh, I was going to suggest the Mexican talavera tiles too!

When you put them all together to preview the designs on a webpage, they can look crazy, but that's not what you're planning to do, so don't let hubby hyperventilate yet! The key is to pick out one or two patterned talavera tile for accents, and then decide upon the solid ground tile color you'll use for the majority of the backsplash. You can do all solid with a patterned tile thrown in here and there, or you can do a patterned block above your sink and stove with solid tiles everywhere else, or you can run a line of patterned tiles midway up the backsplash with the rest solid. You can personalize the layout however you want.

If you do decide to pick out patterned tiles, note that some tiles contain a complete design whereas others are only 1/4 of a design and are made to use in groupings. That sort of design would look awesome above the stove.

Here's a link to the solid color talavera tiles: http://www.tilesandtiles.com/plaincolors/catalogoplaincolors.html

Be sure to see some of these in person, as the patterned tiles are a very distinctive look. Also, make sure you know whether the solid colors will have solid pigment or if a wash has been used. The washed tiles have beautiful color variations, as pigment builds up in some areas but is thinner in others. Do also note that these tiles are often not perfectly flat on top. The irregularities are part of the charm. :-)

The important thing is that something in this design has anything dynamic to say, and so far unfortunately nothing is... thus leaving it to the back splash! It's a great place to have fun though, and I would recommend the use of some very deep, rich, rustic browns, reds, and/or coppers, because I think the multi-colored schemes distract rather than pull together the rest of the pieces in your kitchen. The Mexican tiles references above are definitely beautiful and have the right ranges of colors to select from, just be careful with your contractor to place the patterned ones in exactly the places you want. Doing that wrong (don't let contractor decide) could break the project.

If it were up to me, I would use smaller, consistently colored mosaics, to give the wall a lot of class and character. Maybe the "Red Travertine" or "Rosso Verona" in a square or alternating square pattern:
http://www.bettini.com/marble-mosaics.htm
Your surfaces are slick, give your kitchen some texture along with that color!

This looks very much like my kitchen: white appliances, oak cabinets, yellow walls. I put up talavera on the backsplash and it came out great!