Currently, anything that can be inserted as dynamic text/pictures in data driven pages must be located in the attribute table of the index layer (unless if you have a related attachment table for pictures). My idea is for data driven pages to support dynamic text/pictures from a related table.
Here is my issue. I have thousands of pictures that I need to be inserted into data driven pages. Using the attachment table works, but the size is becoming too large and we need to store the pictures elsewhere. I have the picture filepaths in a related table, but I cannot insert those pictures into the data driven pages via the "Simple path from Data Driven Pages" option due to the fact it must pull from a field within the index layer.
The only work around that I know of is to create the picture fields within the index layer itself, but this is not an ideal option because each record might contain multiple pictures.
I propose that ESRI support related tables in data driven pages.