If you know your teas, then you can tell - just by looking at a
picture of the dry leaf or the infusion color.

Here's an example (and don't tell me it was the lighting that made it
look like this):
http://www.theteaemporium.com/customer/product.php?productid=849&cat=55&page=1

And here's one that looks a little fresher:
http://www.teaopia.ca/products2.cfm/ID/30/c/Loose-Leaf-Green-Tea

Here's another pic of fresh longjing:
http://www.nipic.com/show/1/58/19a4ab832c240337.html

Now do you know?