These are "residual" low spatial-frequency responsivity maps created by 
stack-averaging ~200 scan-collapsed X,Y binned "NEOWISER - ALLWISE" delta
magnitude tables generated during operations per scan. The delta-mag
estimates in these tables are first converted to flux-space, renormalized
to have a spatial-average of unity, then stacked using trimmed averaging
and smoothed using a constant Gaussian kernel to remove the binning pattern.
These products illustrate the performance of the pixel calibrations
(flats, darks, sky-offsets etc.) and hence the quality of the L1b frame
products from which sources are extracted.

The min-max stretch on all jpegs is 1 +/- 0.5%, i.e., 0.995 --> 1.005

F. Masci, 12.17.2014