I am having problems with my lock screen. I had a very old mod which I am trying to replace. I keep deleting it and replacing the lockslider.png with a new one (in /opt/usr/share/themes/alpha/backgrounds). When I replace my old lockscreen my new screen shows on the lock screen. However, each time I switch off my device and switch it back on (which is everyday as I have to charge my battery externally) the old lock screen comes back.

Does anyone know how I can permanently get rid of this lockslider.png which has just refused to go?

I am using WinSCP by the way. I have tried using midnight commander to replace or delate the file but I get a message saying cannot delete file, permission denied (13).