I love this illustration of Wonder Woman sizing up a vastly over-grown Wonder Girl. While Wonder Woman appears to be her normal busty self – perhaps a bit more girlish than normal, Wonder Girl has grown into a huge-breasted, muscular mini-giantess, Their roles would appear to be more than reversed, now, with Cassie possessing vastly greater strength than Diana.
I love how pleased the newly-giantess Cassie appears when looking down (over her newly-grown huge boobs) on the relatively diminutive Diana.
The artist is DogSupreme, who has a quite a comics, manga and anime portfolio on deviantART. Most of it is not growth-related, but there are some quality female muscle growth and breast expansion works in there.
I actually commissioned that one from him. He is Ben Dunn, a comic artist for Antartic Press. My deviantART page has alot more like this that I have commissioned. Feel free to check it out. You may recognise some other ones from around the web that were commissioned by me:
http://bradbarry2.deviantart.com/#