Set Default path for binary field
To fix your problem, please try to set data_dir (like data_dir = /path/you/want) in odoo-server.conf file. Or, you can set odoorc.conf file in home folder.
In odoo, I'd like to set a default path when upload a binary fields, for example when I upload a file the path should be always : "/home/user1/Documents".
Best regards