That should be straight forward as long as you are using the option to add your address dynamically from your database.
Your database (and therefore the recordset on your google map page) would have to contain the filename for the images you want to use. So when you have entered the addresses dynamically on the second screen of the ProMaps interface(as per instructions here), you proceed to the next screen and would select 'custom' from the 'Info Window' drop-down list. You should see the dynamic data already entered for the address fields.
You would then just need to add the line for your image:
<?php echo $row_Recordset1['UserAddress']; ?>
<?php echo $row_Recordset1['UserCity']; ?>,
<?php echo $row_Recordset1['UserState']; ?>
<?php echo $row_Recordset1['UserZip']; ?>
<img src="pathto/yourimages/<?php echo $row_Recordset1['the_image_filename']; ?>">
The images would all have to be the right size on the server, as this would just place the image 'as is'. Digital File Pro could size the image as you want it if you are using that to upload them.
(You could also specify a size in the <img> tag of your code, but unless all of your images' heights are the same prportionally to their widths, you might end up with some squashed faces).