I have 3 year old image hosting web site with huge amount of hosted images. This images is placed all over the internet with bbcodes, like avatar images, funny pictures in blogs, etc. I'm sure for this, because i saw and checked hundred of this pictures (hosted on my server) in many websites. But for google my website have 6-7 links. Why is this?
Perhaps you did a big mistake in the bbcode or html code you give your users. Does it include a link to your site or is is just to display the image? You need a link, otherwise no backlink is counted for just displaying an image from your site.
Yes. I have links over the images. When I say that I checked pitcures - I mean that I check the source code for: <a href="http://www.mydomain.com/page111"><img src="http://www.mydomain.com/page/111.jpg"/></a>
Google doesn't publicly disclose all of your backlinks - only a small fraction of them. Don't worry about it - they know that they're there and they're counting them, even if they aren't showing them... If you want a much better picture of your backlinks, use Yahoo or Alltheweb.