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for those who don't want to winterboard:
go into
/private/var/stash/Applications/MobileSMS.app
then copy and replace icon@2x.png to
/private/var/stash/Applications/biteSMS.app

edit:
also to change the name from biteSMS to Messages, go into /private/var/stash/Applications/biteSMS.app/info.plist and change
<key>CFBundleDisplayName</key>
<string>biteSMS</string>

Thank you! Exactly what I wanted.

I was able to use iFile and make these changes in 2 minutes.
 
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