Given the update note feature, xlslib now has much of what is needed to support images. Excel does not let you put an image in a cell, but you would be able to align images with the top-left corner of a cell.
Also, the .xls format does not let you specify column width in inches or centimeters - they are spec'd in increments of a character from the default font's size. So fully aligning columns to images is going to be hit or miss.
Please add a comment to the Image discussion if interested.