Hmm, there's a small problem with the timings it seems. The script changes the picture ok but it's definitely not obeying the time set in the profile.

Ok, I think I've managed to fix this for the latest versions of Adium... but I know next to nothing about Applescript so you accept that this is at your own risk.

Navigate to the xtra... right click and choose 'Show Package Contents'
Go into the 'Contents' folder, then the 'Resources' folder
Right click on the 'Icons.scpt' file choose 'Open with...' and select 'Script Editor'

Find the line that reads: set «class AusI» of every «class acct» to tifimagedata -- sets the buddy icon
Change that line to read: set the image of every account to tifimagedata -- sets the buddy icon

Click 'Compile' and save the script.

Test it

If it doesn't work now, you may need to open a terminal session and type: touch ~/Library/Preferences/com.adiumX.icons.scripts
That file is supposedly created by the script but I couldn't find it on my system so I created it manually.