Okay, so once the images are located, transferring them via bluetooth to a computer running ubuntu linux is easy. Before you get started, there are a number of tools which you might want to run (such as hcitool) in order to check your device status. These are detailed in the Dialup bluetooth internet connection article.
So to proceed with your file transfers, you will first need to run the gnome-obex-server application like this:
chris@snackerjack-lx:~$ gnome-obex-server
In this case, I am running the application in the foreground - this is so that I can see what's going on as the bluetooth file transfers progress. If I wanted this to run in the background, I would put a '&' character on the end of the command like this:
chris@snackerjack-lx:~$ gnome-obex-server &
Okay, so now I will select a file from the K750i and monitor its transfer progress. This is what comes on-screen under the obex server command:
chris@snackerjack-lx:~$ gnome-obex-server
** Message: Incoming connection from 00:18:13:50:0C:EB
** Message: Device 00:18:13:50:0C:EB is about to send an object.
** Message: File arrived from 00:18:13:50:0C:EB
** Message: Filename 'DSC00298.JPG' Length 59500
** Message: Saving to '/home/chris/DSC00298.JPG'
** Message: Incoming connection from 00:18:13:50:0C:EB
So there you can see the file DSC00298.JPG has been saved into my home directory.. Dead easy!.