$user_IDER = get_current_user_id (); (Here you recover ID, in this case current user)
um_fetch_user ($user_IDER); (Here you set profile IDs for which you want to obtain the url of the avatar)
$avatar_uri = um_get_avatar_uri (um_profile ('profile_photo'), 32); (Here you get avatars of that ID)
echo $avatar_uri; (Here you can see the url of the avatar)
Can this help you?