Hi
I've seperated your question from the thread "Nginx + Moodle configuration tips" http://moodle.org/mod/forum/discuss.php?d=157382 They are simply not the same! Your question may not even be performance related.
Any way, get the second problem, pics not displayed solved first. Your referer URL http://9.1.0.9/moodle/user/files.php looks suspicious to me. Check your $CFG->webroot setting. All these are explained in the docs, http://docs.moodle.org/20/en/Installing_Moodle for example.
Hardware and performance
"file picker" problem and no pics
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