Only links open a new background tab on middle-clicking.
That's how all browsers work.

That site doesn't provide links for the thumbnails.
It also doesn't explicitly process middle-click event.
Report the issue to the programmers/designers of that site.

Yes, many websites are like this one.
Would there be anything wrong with: Upon middle click:
if   ( would do something ) { then do that something }
else                        { do what left click would do }

The behavior you suggest is not implemented in any browser AFAIK, so it'll break the expected behavior if using muddle click to scroll the page when clicking something that's not a link. It won't be helpful anyway on most sites because the thumbnails are small so there's no point in opening them in a new tab. Also, this is something that can be implemented with an extension.

I think this more of the way how the page been implemented then a Chrome bug, Since the same works fine with

https://www.google.cz/search?sourceid=chrome&q=chromium&um=1&ie=UTF-&tbm=isch&gws_rd=ssl#um=1&tbm=isch&q=chrome 

@wox I suppose you mean autoscrolling. And here if you left clicked, you would see it is the link, not the thumbnail the user wants to see. @pbo: are you saying middle click works with Chrome?

#6, the page you've reported doesn't have links on images so there nothing chrome can do. You seem to suggest that chrome somehow guesses the link but it's not possible. Those many sites you've mentioned, how many, and which sites exactly? The really popular major sites like Google images linked above properly wrap thumbnails in links so middle click works correctly. 

OK, looks like a disaster in w3m text browser too.
I guess you are right. One can't bend over backward to fix up each site.

OK close it.

marking the bug as wontfix for, since the page implamentation doesn't support this.