There will be quite big differences between old and new Z4 rear light graphics, yet general shape of cluster stays almost the same.
From the camouflaged (cluster is heavily taped) photo of M4 roadster Klier posted
the following differences can be seen:
- lower lip below the cluster is more refined and continious
- cluster is now even, and no more so "gradely / stagely" shaped; but there is a crease ala in E90 rear light separating position light strip from lower concave part of cluster - for 3D-ish effect
- rear position lights are now done in CELIS-LED ("LED tubes") technology (like on E90 3er), and are shaped as rectangular strip which occupied the upper part of the rear light cluster
- under the position light indicator light is placed, and now occupies the lower outer sector of the cluster (no more shaped as a little circle inside a outer side of the cluster)
- under the position light and just beside indicator light, a brake light is placed (trapezoidly shaped)
- inner of brake light a part of narrow rectangular reverse light (like in 5er's rear light cluster) can be seen; I guess it runs horizontaly, not verticaly
- the part of cluster inner of brake light and under the reverse light is not clearly seen, but I suppose it features a fog light, and perhaps a red reflector
So, the new design of cluster is more sleek and even, and graphics feature more rectangular instead of circular shapes; even more: circular graphics in rear light cluster are gone!