When using the column templates you'll find a type of column that is possible to add to your template called "Media".
The columns belonging to this type, give you the option to upload files to each campaign line, for example, you could upload the images/videos that will be used in your creatives as shown below.
Restrictions:
You can only have one column of type Media per media plan and per Column Template.
The maximum number of files that can be uploaded per line is 20
Each file size should be 50Mb max.