i want to change logo, how should i change it.
Go to the Wiki of pfsense and have a look at the proposed articles.
This just might be it: http://wiki.pfsense.com/wikka.php?wakka=ReBrandingSupport
Good luck ;)
I presume that you want to rebuild it afterwards…. but, please. Don't.
If you couldn't find the link in this post - then please note that rebuilding pfsense is another ball game yet :)
Although, it is possible.