I don't think there's a setting to specify new releases. They do probably go off of the available date in Advanced, so maybe you could fiddle with that date to get the ones you want to show.
I usede the Advance tab date. Then I have a category for Recently Added Items. When I import my products they are putin that category, or I can manually change a product date.
You can check my Cross Stitch category of products - the Recently Added Items is the very first category in the cross stitch product category list.