Well, since no-one else reacted let me have a go at it ...

Here is a Javascript that lets you save a report for all used image file names and the size of the rectangle it is placed in (note that it is possible this is not the "image size used"!).

//DESCRIPTION:Write image size report
// A Jongware Script 12-Apr-2012
res = [];
imgs = app.activeDocument.allGraphics;
unitname = getCurrentUnit();
for (i=0; i<imgs.length; i++)
{
  h = imgs[i].parent.geometricBounds[2] - imgs[i].parent.geometricBounds[0];
  w = imgs[i].parent.geometricBounds[3] - imgs[i].parent.geometricBounds[1];
  // some fair rounding
  switch (unitname)
  {
    case 'in': w = w.toFixed(3); h = h.toFixed(3); break;
    case 'cm': w = w.toFixed(2); h = h.toFixed(2); break;
    default: w = w.toFixed(1); h = h.toFixed(1);
  }
  res.push (imgs[i].itemLink.name+'\t'+w+' x '+h+' '+unitname);
}
defaultFile = new File (Folder.myDocuments+"/"+app.activeDocument.name.replace(/\.indd$/i, '')+".txt");
if (File.fs == "Windows")
  writeFile = defaultFile.saveDlg( 'Save report', "Plain text file:*.txt;All files:*.*" );
else
  writeFile = defaultFile.saveDlg( 'Save report');
if (writeFile != null)
{
  if (writeFile.open("w"))
  {
    writeFile.encoding = "utf8";
    writeFile.write (res.join("\r")+"\r");
    writeFile.close();
  }
}
function getCurrentUnit ()
{
  switch (app.activeDocument.viewPreferences.horizontalMeasurementUnits)
  {
    case MeasurementUnits.POINTS: return "pt";
    case MeasurementUnits.PICAS: return "pt";
    case MeasurementUnits.INCHES: return "in";
    case MeasurementUnits.INCHES_DECIMAL: return "in";
    case MeasurementUnits.MILLIMETERS: return "mm";
    case MeasurementUnits.CENTIMETERS: return "cm";
    case MeasurementUnits.CICEROS: return "c";
    case MeasurementUnits.AGATES: return "ag";
    default: alert ("Oh, come on!"); exit(0);
  }
}