One option would be a Bluetooth File Transfer app.
As alternative, you could try an Android FTP Server app which would work via a network connection.
Once you have an SFTP
Server running on your phone, you can use the FTP
protocol to download your pictures.
The format of the URL to be entered in your Chromebook browser:
ftp://username:password@example.com/test/
Make sure that you don't run this FTP
server too long or too ofter as FTP
tends to be a popular security hole. More secure would be SFTP
.