Well it may be signed or it may not be signed at all, but what's important it works and this is by far the easiest. Many have used this way to recompile framework-res or systemui. My modded apk.
Here: http://www.androidgamehacks.net/foru....php?tid=18297 (this is the same except he change the files to be copied into)
This method like I said, doesn't sign it but rather keeping the original signature for the newly modified apk. Maybe what I wrote before is not really accurate and it cause confusion and for that I am sorry. Well it's up to you, there are many ways and this is one of them. Just telling.
This is "jarsigner -verify -verbose " log for your apk
jarsigner: java.lang.SecurityException: SHA1 digest error for res/anim/accelerate_decelerate_interpolator.xml
sm 5306 Fri Nov 30 00:00:00 IST 1979 assets/images/android-logo-mask.png sm 641 Fri Nov 30 00:00:00 IST 1979 assets/images/android-logo-shine.png sm 79471 Fri Nov 30 00:00:00 IST 1979 assets/sounds/bootanim0.raw ... sm 635 Fri Nov 30 00:00:00 IST 1979 res/raw-zh-TW/loaderror.html sm 859 Fri Nov 30 00:00:00 IST 1979 res/raw-zh-TW/nodomain.html sm 959 Fri Nov 30 00:00:00 IST 1979 res/raw-zh-TW-xlarge/incognito_mode_start_page.html s 334202 Fri Nov 30 00:00:00 IST 1979 META-INF/MANIFEST.MF 334255 Fri Nov 30 00:00:00 IST 1979 META-INF/SONY-ERICSSON-E-PLATFORM-SIGNING-LIVE-864F-3.SF 1375 Fri Nov 30 00:00:00 IST 1979 META-INF/SONY-ERICSSON-E-PLATFORM-SIGNING-LIVE-864F-3.RSA s = signature was verified m = entry is listed in manifest k = at least one certificate was found in keystore i = at least one certificate was found in identity scope jar verified. Warning: This jar contains entries whose certificate chain is not validated. This jar contains signatures that does not include a timestamp. Without a timestamp, users may not be able to validate this jar after the signer certificate's expiration date (2035-01-01) or after any future revocation date. Re-run with the -verbose and -certs options for more details.
I don't know what must be signed and what is not, and you probably can trick it to have untouched resources signed. but anything you change will not be signed.