  An important contribution to the gamma-ray emission of our Galaxy is the
Galactic Diffuse emission. We present specific developments within the PICARD
code for modeling of Galactic cosmic ray propagation that are relevant for the
computation of the gamma-ray emission to accommodate a new Interstellar
Radiation Field (ISRF) model. We study the differences of the individual ISRF
models on Galactic Diffuse gamma-ray emission predictions in the GeV to the TeV
energy regime. Emphasis was laid on obtaining robust predictions for observable
signatures in the very high energy gamma-ray regime with a special attention to
the energy regime for H.E.S.S. Preliminary longitude-latitude profile and
residuum maps of inverse Compton emissions are shown for axisymmetric and
four-arm spiral Galaxy models.
