How change user_picture when using Imagecache Profiles?

Hi,

I have two little PHP questions to the module. When using the block "Latest visitors" in a profile-page the userpictures should be a different size than the size of the profile-picture.

Is there a chance to change the behaviour of the pictures? I am using Image Cache Profiles with an preset: user_image_large for the user on his profilepage and an preset: user_image_default for comments, advanced forum, articles and so on ...

So is there a PHP possibility to change the line:
$output .= theme('user_picture', $account);
in the function theme_user_visits ???

to see there the user_image_default?

And my second question is also a PHP Problem .... When I don´t want to use the blocks, because of an own themed profile-page ... what is the correct PHP - Order to get the last visitors shown in the profile-page?

With print_r ($account) I could see the [user_visits] => Array ... but I am not to good in PHP - Can you give me a hand to get the last visitors shown, without a block?

THX