var
  X, Y: Integer;    // column and row iterators
  DstArea: TRect;   // destination area
  Margins: TSize;   // calculated margins between images
  ImgSize: TSize;   // size of a single image
  ImgOrig: TPoint;  // target image origin
  CntCols: Integer; // actual number of columns
  CntRows: Integer; // actual number of rows
  MaxRows: Integer; // maximum number of columns that can be placed in the area
  MaxCols: Integer; // maximum number of rows that can be placed in the area
begin
  DstArea := ???;

  MaxCols := ???;
  MaxRows := ???;

  ImgSize.cx := ???;
  ImgSize.cy := ???;

  CntCols := Min(DstArea.Width div ImgSize.cx, MaxCols);
  CntRows := Min(DstArea.Height div ImgSize.cy, MaxRows);
  Margins.cx := (DstArea.Width - (CntCols * ImgSize.cx)) div (CntCols + 1);
  Margins.cy := (DstArea.Height - (CntRows * ImgSize.cy)) div (CntRows + 1);

  for X := 0 to CntCols - 1 do
    for Y := 0 to CntRows - 1 do
    begin
      ImgOrig.X := (X * ImgSize.cx) + ((X + 1) * Margins.cx);
      ImgOrig.Y := (Y * ImgSize.cy) + ((Y + 1) * Margins.cy);
      
      SomeCanvas.Draw(ImgOrig.X, ImgOrig.Y, SomeImage);
    end;
end;