They are all that same Sand bitmap. Only two of the files actually reference it. In all of the others, it's there spuriously. Sometimes it's in there twice, and makes the file a lot larger than it should be.
Here are the references:
Cacho_score.svg: xlink:href="#sand_bitmap" Cacho_score.svg: xlink:href="#sand_bitmap" Dinogetia_Garvani-_layout.svg: style="fill:url(#sand_bitmap);fill-opacity:1;fill-rule:evenodd;stroke:#000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" /> Dinogetia_Garvani-_layout.svg: style="fill:url(#sand_bitmap);fill-opacity:1;fill-rule:evenodd;stroke:#000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1" />
It should be removed from the files except for those two (a SED script would work, or XSLT, or hand editing).
If you want to dig further, you can look for image tags in SVG, reject all lines containing the "provided by" string, and see what the others are.
I'll see if I can make a current version of Inkscape leave them in a file when they aren't referenced.
Thanks
Bruce