3000+ images browser crash

I tested CKFinder (2700 images) on my local computer and it took less than 2 seconds just to generate list of files on the server side.
Displaying it in browser took 25 seconds (Firefox) and 8 seconds (IE).

Is your computer old? Maybe the server is overloaded?
Open Firebug (in Firefox) to trace ajax calls, you should see "GetFiles" request there, something similar to that:

http://example.com/ckfinder/core/connector/php/connector.php?command=GetFiles&type=Images&currentFolder=%2F

This problem can be solved only by adding new functionality to the CKFinder, so I'm adding this to the potential list of new features.

For now, you can try "optimizing" the GetFiles command (core/connector/php/phpX/CommandHandler/GetFiles.php).
I'm unable to test CKFinder on your server with xdebug, so I don't know what makes this request so slow, but I think you can try to replace this

$filemtime = @filemtime($_sServerDir . $file);
$size = filesize($_sServerDir . $file);

with:

$filemtime = 1204050676;
$size = 128;

for example when sizeof($files) is more than 200. Test this and compare the speed results (I assumed that the problem is with thousands of file operations made by this script, so this should work faster in this case).

Remember that this is just a quick hack that will cause sending wrong size of files and invalid modification time.
To speed up sending of the XML responses, you may install mod_deflate or mod_gzip to compress the output.