Giving your smartphone a facelift by applying a new theme has always been a popular (and often free) option. With the change in official Symbian icon set for Anna, giving your phone the 2011 'look' has never been more appropriate. Even if your smartphone was created in 2008.
Publishers MMMOOO are perhaps the best place to start, since their themes are as official as you can get, being used in some of Nokia's product materials. I made a beeline for 'Glows Symbian Anna', since it looked like it was dark enough to work well on my N86's AMOLED screen and yet still have plenty of attractive colour to it.
Searching for 'Anna' in the Store client is a good start. Some S60 5th Edition models are mentioned but many 3rd Edition ones also work fine.
And here the theme is, in action. Anna on 3rd Edition does go. Well, the theme parts of it, at any rate!!
The theme also includes such items as backgrounds for use in certain applications, e.g. here in Music player.