I think having a latest classifieds page would be more convenient than random classifieds, just to see what's new in the selling section, would be easier!
When you go into the classified section, the adverts at the top are the newest ones (as long they had a picture added). I do agree that the ones on the main page should at least be picked from the most recent ads as it always seems to be the same ones that show up that've been there since Adam was a boy.
I think having a latest classifieds page would be more convenient than random classifieds, just to see what's new in the selling section, would be easier!
as it is though some thing might pop up thats been there a while and you have missed it or didn't need it at the time.
to find all the latest you can go in to classifieds and click ads posted in the last day, last 7 days, last 14 days. just under the search box