Maps are made with SANEPIC (Patanchon et al. 2008) by Viktoria Asboth (UBC;vasboth@phas.ubc.ca).
250, 350, and 500um are labeled PSW, PMW, and PLW, respectively.  
Each map file contains three extensions: 
1) sky, in units of Jy/beam
2) noise, in units of Jy/beam
3) hits, i.e., the number of times the pixel was observed.

To convert to Jy/sr, maps must be color corrected and divided by the solid angle of the beam.  
Color correction depends on whether the source is point-like (i.e., non-local galaxies) or diffuse (i.e., Galactic cirrus or the CIB).  
This correction is detailed in the SPIRE Observers Manual (http://herschel.esac.esa.int/Docs/SPIRE/html/).  
For extended sources, color correction is shown to be negligible (Viero et al. 2013b), thus dividing by the solid angle is all that is needed to convert to Jy/sr.

The SPIRE beams have FHWM: 18.1, 25.2, 36.6 arcsec and 
effective solid angle of :(1.05, 1.73, 1.69)x10^-8 steradians at 250, 350, and 500um, respectively.