I have to say, that is a somewhat unusual looking litter.

I have seen my fair share of Triamese, but none with back stripes quite that dark. Usually their stripe is a pretty light (almost) beige. Something also strikes me as odd with the appearance of a high white mark on some of their heads.

Also, unless it's your camera, the Siamese seem to be a bit darker than most.

In conclusion, if you twisted my arm, I'd say Triamese and Siamese. They just might be darker than most. This might just be one of those wait and see litters.