After more than half of year after noticing the issue and getting frustrated with the "can't set new Yahoo! avatar in Pidgin" bug, it seems that things have finally gotten a move on!
Testing whether the avatar updates for the Yahoo protocol in Pidgin 2.5.4 -- this finally works, with no other user intervention! Just go to Accounts >> Manage accounts and change the display picture.
However, the previous version of Pidgin that I used, 2.4.1, didn't do that automatically. To sum it all up:
The workaround for the avatar not updating for the Yahoo! protocol for Pidgin builds prior to version 2.5.3, was to:
- quit pidgin;
- edit ~/.pidgin/accounts.xml, where I removed the values attached to the Yahoo! account, for the following settings: picture_url, picture_checksum, buddy_icon, picture_expire, and buddy_icon_timestamp.
The next time I ran it and set a picture, the values for the settings mentioned above were computed instantly and handled properly.
Also, the picture displayed as the user avatar on the Yahoo! servers looked fine: http://img.msg.yahoo.com/avatar.php?yids=Your_YM_ID_here.