sites/subDomain/libraries doesn't load the library files My website has two sub-domains, I need to install imageFlow library in both of these sub-domains but for some reasons I need to replace default images of imageFlow (I mean slider.png, button_play.png and button_pause.png) library in sub-domian1 with some images and in sub-dmoin2 some other pictures. To do so I created folders sub-domain1/libraries  and sub-domain2/libraries and I copied the modified version of the imageFlow in there. But unfortunately it doesn't work and imageFlow is not loaded. If copy the imageFlow library in sites/all it works well but in this way the same version will loaded for all sites.
I think you would want to keep the imageFlow library itself in the sites/all/libraries folder, then to adjust the images for each site, modify your theme to override the default css and images of the imageFlow library. You could do this by copying the imageflow.css stylesheet into your theme, including it, then modifying it to point to custom images instead of the imageflow default images.

This would be a little bit more standard approach than changing the imageFlow source files.