i recently tried to test the anti theft by installing a different sim card. the alarm was set off as expected. but one thing surprised me was the background wallpaper. it showed my ex girlfriend’s caller id pic :o
it was the only caller id pic on my contact list. that might be why it was shown when the alarm was set off. so i deleted it from her contact details. and added another caller id pic to another contact. but the background wallpaper still didn’t change when the alarm was set off. it still showed my ex’s pic :-[ it makes me feel like she kept coming back and tried to hunt me down 
how can i set this background wallpaper? is there any way to change it? :-\
Well… What I can say it is not avast Mobile Security or the AntiTheft the programs which are changing the wallpaper…
don’t scare me. it wouldn’t be my ex doing it, rite? lol
anyway, probably i didn’t give enough detail of the problem. it’s not the wallpaper of the phone during normal use that was changed. it’s just the background picture when the alarm goes off. here’s what it does:
after a different sim card is installed and the phone is turned on, the siren goes off, the phone is locked, and there’s a box for me to enter the password to unlock the phone. this is when the screen background is changed to my ex’s caller id pic. once i entered the correct password, the phone is unlock, then the screen background is changed back to normal (NOT my ex’s caller id pic any more).
Did you set her phone number as one of the “friends” number to alert when the phone is stolen (into avast! AntiTheft settings)?
i never set her number in the list. it only has my brother’s number and my second number.
My guesses got empty…
so uninstalling the program might be the only way then?
In the computer world, the way uninstall and reinstall is almost a panacea 
too bad for this problem, “uninstall and reinstall” is no cure. i tried doing it several times already, cleaning avast data from phone and sd card. i even deleted the caller id pic from the phone. but it still shows up in the background whenever the alarm goes off. :-[
we are using the system pic that is defined for that purpose. seems like either your android os got somehow corrupted, or the pic is still set somewhere in the settings.