Palletizing Bulk Tiled Imagery

[Dustin Moore]

Is there a procedure involving FOSS tools like GDAL or ImageMagick that
can take a collection of tiled 24 bit GeoTIFFs, come up with an average
best fit pallette, and then dither the TIFFs using that pallette? I see
that there is a program called rgb2pct.py in GDAL but that doesn't allow one
to specify a universal palette.

Lastly, is there a FOSS tool that can take a collection of tiled TIFFs
in one projection and then reproject/retile the TIFFs in another projection?
I've worked with gdalwarp on a per-tile basis but that makes the output
tiles parallogrammed as per the re-projection and this causes me trouble when
I go to seamlessly composite the new tiles back together. (Actually, the problem
is with gdaladdo and how it interpolates NODATA elements into the overviews but
I'd rather just get the tiles square and not have any NODATA/edge problems possible.)

Dustin Moore