  The origin of the inner Galactic emission, measured by COMPTEL with a flux of
$\sim ~ 10^{-2}$ MeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ in the 1-30 MeV range, has
remained unsettled since its discovery in 1994. We investigate the origin of
this emission by taking into account individual sources which are not resolved
by COMPTEL and the Galactic diffuse emission. The source contribution is
estimated for sources crossmatched between the Swift-BAT and Fermi-LAT catalogs
by interpolating the energy spectra in the hard X-ray and GeV gamma-ray ranges,
as well as unmatched sources. This results in a flux of $\sim$20% of the
COMPTEL excess. The Galactic diffuse emission is calculated by GALPROP to
reconcile the cosmic-ray and gamma-ray spectra with observations by AMS-02,
Voyager, and Fermi-LAT, resulting in a flux of $\sim$30-80% of the COMPTEL
emission. Thus, we show that the COMPTEL emission could be roughly reproduced
by a combination of the sources and the Galactic diffuse emission. Furthermore,
combined with the extragalactic emission, we construct all-sky images in the
MeV gamma-ray range to pinpoint some potential interesting targets for future
missions, which would be critical for bridging the MeV gap in the spectra of
gamma-ray sources.
