One option would be to uncheck "Enable user pictures" in account settings and add your own custom imagefield. Then you should be able to enable alt and title fields in the field settings. You can also use this field in views.

You would need to override this function in your template.php file and override the alt tag.

Another option would be to uncheck "Enable user pictures" in account settings and add your own custom imagefield. Then you should be able to enable alt and title fields in the field settings. You can also use this field in views.