With the switch to GTK+ 3.x, most theme engines no longer work, and I personally only know of 3 (Adwaita, Unico, and Solidity).
What engines are available for use with GTK+ 3.x?
You have identified most of the engines ported (at the time of writing) to the full gtk3+ API.
In addition, there is 12.04 KDE support for oxygen-gtk3 (or for 11.10 via kubuntu-ppa-backports)
Arch has an gtk3-xfce-engine but this has yet to be packaged for Ubuntu.
Various references on google report that the development of the gtk3-engines package has ceased - not all the engines in the package were fully ported to GTK3+
For reference only: according to the notes of the gtk3-engines package in the ppa:gnome3-team/gnome3 - these were attempted to made available BUT don't expect these to work fully on oneiric.