Create a COM server once, iterate over the images and place them in the desired cells, quit the server and then delete the server object.
Building from my previous answer, here is a working example with 5 of many built-in images:
%Some sample images
im{1}=imread('peppers.png');
im{2}=imread('cameraman.tif');
im{3}=imread('pears.png');
im{4}=imread('greens.jpg');
im{5}=imread('bag.png');
excel = actxserver('Excel.Application'); % Create server object
excelWorkbook = excel.Workbooks.Add(1); % Add a workbook
excelSheet = excel.ActiveSheet; % Get the active sheet
f = figure('visible','off'); % To not show the images in MATLAB
dpi = get(groot, 'ScreenPixelsPerInch'); % Get screen dpi
for k=1:5
imshow(im{k});
print(gcf, sprintf('-r%d', dpi), ... % Print the figure at the screen resolution
'-clipboard', '-dbitmap'); % to the clipboard as a bitmap
%Adjust the cell names where you want to paste the images as desired
excelSheet.Range(['B',num2str(k)]).PasteSpecial();
%Unlocking aspect ratio to adjust height and width of the image according to the cell
excelSheet.Shapes.Item(k).LockAspectRatio='msoFalse';
excelSheet.Shapes.Item(k).Width=excelSheet.Range(['B',num2str(k)]).Width;
excelSheet.Shapes.Item(k).Height=excelSheet.Range(['B',num2str(k)]).Height;
end
excelWorkbook.SaveAs('figtest.xlsx'); % Save workbook to a file
excelWorkbook.Close(); % Close workbook
excel.Quit(); % Quit server
excel.delete(); % Delete server object
which gives:
