[weedahoe]

This may work for what you are trying to do. However THIS particular edit is for the LOWBATT alert. You will need to browse through the folders in the last part of the directory to find the one for the Voicemail Alert and change the script there. As for adding images to the text background, I included that alsoi. However, since you are asking about .gifs, I assume you are asking because you want something animated? I dont think that will work but you can try. Lemme know if it does work for you.

Customize 'Low Battery' alerts

Browse to
HKEY_CURRENT_USER\ControlPanel\Notifications\{A877 D663-239C-47a7-9304-0D347F580408}\
Create a String value named "Default" and set its value to "Low battery warning".
Now go to Start > Settings > Personal tab > Sounds & Notifications applet > Notifications tab, select "Low battery warning" in the "Select an event" drop-down list and you can customize it.


Add background images to alerts

You can use this tweak for different alerts such as call Alert, errorbox, informationbox, questionbox, exclamationbox, dail, log, start, volume dialog etc.

i am describing the process for the call alert only, the rest is the same for all above mentioned items.

HKLM/software/microsoft/shell/Rai/CallAlert

1) create string key named BKBitmapFile and in value define jpg file name with full path
2) create dword key named BKFlags and set value 26
reboot your phone

now when you will receive a call the image you defined will be in the background