I am not an expert on BuddyPress specifically, but I believe that BP has a specified function :
<?php bp_member_avatar('type=full&width=125&height=125') ?>
you can also ovverride by adding code to a functions file or add a file bp-custom.php to the wp-content/plugins folder to change image sizes
Avatar specific settings can be changed:
define ( ‘BP_AVATAR_THUMB_WIDTH’, 50 );
define ( ‘BP_AVATAR_THUMB_HEIGHT’, 50 );
define ( ‘BP_AVATAR_FULL_WIDTH’, 150 );
define ( ‘BP_AVATAR_FULL_HEIGHT’, 150 );
define ( ‘BP_AVATAR_ORIGINAL_MAX_WIDTH’, 640 );
define ( ‘BP_AVATAR_ORIGINAL_MAX_FILESIZE’, $max_in_kb );
define ( ‘BP_AVATAR_DEFAULT’, $img_url );
define ( ‘BP_AVATAR_DEFAULT_THUMB’, $img_url );
So try tot change those settings and see if it helps
EDIT
you can try to use bp_get_member_user_id()
or bp_the_member()
- bp has some kind of "custom-loop" that goes something like this :
<?php if ( bp_has_members( '' ) ) : ?>
<?php while ( bp_members() ) : bp_the_member(); ?>
<a href="<?php bp_member_permalink() ?>"><?php bp_member_avatar('type=full&width=125&height=125') ?></a>
<?php endwhile; ?>
<?php endif; ?>
but in any case, try first to ovveride the defaults like described above, it will also help to identify the problem source .