  We discuss how the propagation of electromagnetic fields described by a
general two-parameter lagrangian, which contains the Euler-Heisenberg effective
lagrangian and the Born-Infeld lagrangian as particular cases, is affected by a
pair of parallel plates that impose boundary conditions in the quantized field.
We consider three differents setups, namely: (i) two perfectly conducting
plates; (ii) two infinitely permeable plates and (iii) a pair of plates in
which one of them is a perfect conductor and the other has an infinite magnetic
permeability.
