I wrote a script (using Archive::Tar) (Sorry can't get to it from this machine) that packagages files into a tar file(tgz is possible), renames this to "BM6", packs it into a Tar::Archive, modifies it to get a valid BMP-Header and finally converts it to XPM-Format.

End of long story: XPM-Files are text and can be posted.
If the package is uncompressed, you can use any suitable Imageeditor to convert it back, else you can find that if the checksum fails you wont get at the second header (because it is compressed) and so must use the same program (Imagemagick) to convert it back.