The Pharo Smalltalk distribution now includes Polymorph - a UI framework with theming including Vista, Windows, Squeak and Watery look. The default Squeak look is/was not very attractive.
But facelifting of the default Squeak UI in the trunk development stream is now also discussed on the Squeak developer list.
And Cincom Smalltak got a facelift too with a fresh UI for ObjectStudio and VisualWorks.
And VisualAge Smalltalk provides modernized browsers.