Can you have any face on the Nike Apple Watch 6 or only the Nike faces ?

Nike has access to all the regular watch faces.

The Nike is a regular Apple Watch with the addition of a Nike watch band, a Nike watch face, and the Nike Logo. Everything else is the same as a regular Apple Watch.

You can use all the faces that the other watch models have as well as the Nike ones.

Every Apple Watch face will be available to you.