Hi,
I would use Media Library, you can setup centralized location for files on both sites. Please note if you want to use images, some adjustments will need to be made to default product images. Currently they are stored as a file, now you need to change form control to read Media Library file.
Check in here how you can setup a custom path for Media Library:
https://docs.kentico.com/display/K8/Configuring+media+libraries#Configuringmedialibraries-Configuringcustomstorageformedialibraries
Hope this helps.