OK. Using folder.txt did the trick. I got almost what I needed. Now the logo image is placed above galleries thumbnails. Though one issue remains. I mean the text /Welcome to the TinyWebGallery/ that appears just above my logo. Digging in the file language_en.php helped me to find out that I can override this label by my own one if I change the value of the variable $lang_titel. But if I leave the variable empty the default text remains. Now I'd like to remove this label from the view. How can I do this right, so that to keep the gallery site title available to search robots. My site will be registered in russian search engines, and the site has to have both russian and english titles.
Thanks.
BTW, TWG is a very nice gallery. I spent much time searching for a good gallery program. And I think TWG is just what I need.