Is your table similar to that in the photo as well? For me what I don't love about the mix of your current chairs with the dark parsons chair is the different styles (as opposed to when you mix styles as between chair and table which I do like). With your existing chairs, I would mix in another modern chair like a Bertoia-style chair.

I like mixing chair styles. For the ends I like armchairs. The bertoia is a good choice. Other options, the Cherner, the Tolix, eames, ghost. Maybe a different material like metal is best to avoid wood clashing.

You can definitely mix different styles as long as there's some sort of flow. In this case, the nail head chairs you posted don't work well with your existing chairs. I do like the idea of upholstered chairs though. Here are some examples that could work. West Elm and IKEA.

I like Lydia's ideas if you want upholstered head chairs since they have a more modern vibe. I especially like the last two if they come in a dining chair height/version.

I agree with Brenda and APM Architecture. I love the wood bench idea with your contemporary set. Your existing chairs are great, but you need some continuity with your new pieces. What about carrying over the cream leather upholstery into a new style. Here are a few options.

http://www.furniturechoice.co.uk/Dining-Room-Furniture/Leather-Dining-Chairs/Ivory-and-Cream-Leather-Dining-Chairs/Perth-Ivory-Leather-Dining-Chair_150123.htm
http://www.furniturechoice.co.uk/Dining-Room-Furniture/Leather-Dining-Chairs/Ivory-and-Cream-Leather-Dining-Chairs/City-Ivory-Leather-Dining-Chair-(Oak-Leg)_105014.htm
http://www.fads.co.uk/dining-chairs/leather/lucy-cream-faux-leather-dining-chair

Also, you don't want anything too living room-y. If you have modern chairs around your dining table, you definitely don't want to pair it with something that looks more like a lounge chair you would use to curl up and read a book.

Personally I would like to see one of two things happen: A) the 2 chairs in the photo in white (to ge some form of "match") OR B) The chairs in some form of funky colour - like purple - really spice things up. I'm not fond of working with white+wood and then mixing in a "black". If you wish to spice it up with a different style AND colour then go FUNKY colour - teal, purple, red - something exciting that will make people forget that the style is completely different. It will be the colour they remember and not whether or not the legs match.

what have you decided to do meinu76?

meinu76? ...

If you want a more serene and calm feeling, make all the chairs the same. If you want a jumpy, staccato-type feeling, mix the chairs

I think that you can mix the chairs but not feeling the two chairs that you posted.

You have a high-end table and chairs. Mixing different woods and end chairs is fine, so long as the end chairs are of the same "class" as the rest of the chairs. (There! I said it!)

we finally decided on the calligaris bess gummy armchair
http://www.smartfurniture.com/content/images/thumbs/0032678_calligaris-bess-armchair_300.jpeg

Looks like those will go great with your existing set! Great choice.

Much better, those will be great.

I wouldn't really mix wood with another type of wood, but mixing it with metal or acrylic like what APM architecture suggested will be nice especially if your dining area is in a modern style. We supply chairs like those by the way.

Great choice!

I personally do not like the mix of those two styles

J Design Group, Modern Interior Design Firm in Miami, Florida - Contemporary Miami Interior Designers http://www.JDesignGroup.com