I have a Content Query Web Part in the home page of my site root that points to a announcement list in a sub site.
Is it possible to also show the new item notification image as the announcement list?
I am using SharePoint Standard 2010.
The new Item notification is configurable at the farm level (default is 2 days) via (from MSDN, valid for SharePoint 2010 too, http://support.microsoft.com/default.aspx?scid=kb;en-us;825510&Product=spts&wa=wsignin1.0)
Using this concept you could envision creating a new calculated property of type Boolean, e.g. IsNew to calculate a difference in Days and if greater than 2 to be set to True (it could also be done without the new column, by calculating this difference in XSLT directly).
A 2nd step is to update the Content By Query Web part XSLT (your own copy of the default ItemStyle.xsl in the Styles Library - i mentioned copy because it is not a good practice to change the default one, but rather to copy-it, change it and after exporting your CQWP from the page, changing the resulting XML to point to the new XSLT) to take into the new column and toggle visibility on the image.