If someone wants to give it a try, here are some idea.
Backend:
- a new check box (Mark Product as NEW) and 2 input boxes (From To). This can be done using jQuery Data Picker (data range):
http://jqueryui.com/demos/datepicker/#date-range. In General Setting you have to set up the time by default, let's say 30 days in case you mark a product as NEW but no range is defined.
Frontend:
- php file extracting from database the range a product should be marked as NEW. if no range, you can use by the default specified in General Settings.
- template file - if product is new, use some graphics to show the product is NEW. Over the product image using CSS, inline, how do you prefer.