The cell array does not include any meta-information, like field name or file name. If you want access to that information you'll need to change your data storage structure. Some options include:
Scalar Structure Good for when there is a single name to reference.
images.red = imread('redsquare.bmp');
images.blue = imread('bluesquare.bmp');
Use fieldnames(images)
to get the names.
Array of structures A little bit more general. Allows completely general names (including special characters and spaces) and additional metadata if you need it (like "size", "author")
images(1).name = 'red';
images(1).im = imread('redsquare.bmp');
images(2).name = 'blue';
images(3).im = imread('bluesquare.bmp');
Use {fieldnames.name}
to get just the names.
Containers.map
Probably more than you need here, but good to know about. help comtainers.map
for more.