I don't know what you mean when you say "How do I download these photos to a local geodatabase on my server machine (not AGOL)?"
Were you serving the Feature Service from your own ArcGIS for Server instance and don't know how to pull the attachments back down?
Is the Feature Service on AGOL and you want to download it and then upload it to your own ArcGIS for Server instance?
Can you be a little more descriptive with your problem statement? Where is the service being hosted, AGOL or your own Server?
Here's the workflow to download a layer to a local file geodatabase on AGOL. If it has attachments, they'll come with that File Geodatabase.
- Go to the Item Details page of the layer in the Web Map which you were editing through Collector and adding attachments to.
- You should see an Export Data button.
- Click it and select the option Export to FGDB.
- Enter a Title, Tags, Summary and select the folder in your My Content directory you want the File Geodatabase saved to, then click Export.
- Once the Export is complete, you will be redirected to the Item Details page of that new File Geodatabase.
- Click the Download Button
- Open your new File Geodatabase in Desktop and enjoy.
Now, if you want to them deploy that to your own server as a service, then it would just be a matter of loading up the feature class in ArcMap and publishing a new service.