Gordon answered you about the spiral and how to change that, which it seems you've already accomplished - good for you.
But on the second part where you want to tag things in addition to Sale - it is more than just the graphic. In order for the sale tag to appear you need to place the item on sale - this flags a field in the database and the code knows this and displays according to all the css coding.
In order for you to use this type of method for other tags you would need to add fields and css coding and add an entry point in the admin panel for each type of flag.
Here's some alternative ways that don't require code and database change that might work for you:
There is a section in the home page titled Latest - you could emboldened that area with descriptors after the Latest Products tag, you can also change it to say NEWEST PRODUCTS or whatever term you wish.
You could also simply put your own NEW tag with the product description - this would not show up on the home or categories pages, just the product page.
Lee