photons - Deriving Planck's radiation law from microscopic considerations?

In the usual derivation of Planck's radiation law, the energies or frequencies $\omega$ of the oscillators depend on the measurements $L$ of the black body. The model is such that the only characteristic energy is given by these oscillator excitations and in terms of the temperature $T$. Also, the oscillation amplitude vanishes on the walls. Specifically, the structure of the atom walls doesn't enter the computation. After all, that's pretty much the definition of a black body.

My question:

Are there computations (maybe QED + statistical physics?) for more realistic systems, which might model the interaction of photons with the wall atoms and which give results such that one can see the limiting case to an ideal black body?

The question came up when I wondered about the theory behind emission and absorptions of photons on the walls of a black body.

Answer

Worrying about the walls can be misleading. See

A blackbody is not a blackbox

for an illuminating account of the derivation of the Planck spectrum without enclosing the field in a box. If you cant get the published version, see the arxiv version.

EDIT (25 March 2012)

Planck's Radiation Law: A Many Body Theory Perspective

discusses blackbody radiation from a many-body viewpoint. Note that they also consider interactions among the photons and electrons, and still show Planck's law is valid. This might perhaps be considered as arising from the interactions of the photons with the electrons in the walls, if you like. This paper is, of course, also referred to in the first paper I mentioned.