Help: sidebar, more visibility for the latest post, gif icon

Hi, my first post here and I hope this is the right subforum for my question, in case feel free to move it.
I’d need need help to add a little gif (saying something like “new”) to give more visibility to the latest post in a sidebar of a static wordpress home page.
Basically in this sidebar I’d like to have a few recent articles’ titles, and this icon showing only for the latest one (automatically).

Of course I can use the recent posts or the feed widget but those don’t let me add this little image, so I guess I should add some lines of code in my sidebar page.

Please have a look at this example, it looked to be what I’m looking for:

http://www.seoadsensethemes.com/putting-a-new-post-image-label-next-to-entries-wordpress-posted-last-24-hours/

But I can’t get how to make it work, where to put this code, and the demo doesn’t work anymore.

Could you help me please?
p.s: I cannot upgrade to 3.0 at the moment.

Thanks!