For example is there any servers with photos with Creative Commons licence? And not only some general photos but, with concrete objects (people, buildings, pictures etc.). And if I find a picture on a site (for example search in Google) how can I find its licence? I am interested especially in photos or famous people, but not only that.
If not stated differently, websites contents (this including photos) must be considered copyrighted by the owner/maintainer of the website and you can't use them straight away.
It is always a good (and nice) thing to ask the owner/maintainer for licence term and/or permission to share that photo on Wikipedia.
Google allows to filter the results based on the licence (append to the URL the following
&tbs=sur:f ) but also stated "Images may be subject to copyright." so you shouldn't exclusively rely on it.
Most photos on Wikipedia (or Wikimedia Commons) are either created for that purpose, and thus licensed appropriately, or are found from Flickr, which allows and encourages users to add Creative Commons licenses to their photos.