So I've spent the evening working on the UI for the 1.2 version of Terrarium. (This is the version built on .NET 1.1 and will sync with the release of the source code).  At first I was going the Photoshop route for the buttons, etc. but realized that I could do much of what I was doing just using GDI+.  So here is a screen shot of tonight's progress:

Obviously the UI is just laid out in “skeleton” mode right now, with none of the Terrarium functionality hooked up to it.  I also need to create some icons for a few of the items.  It supports a very basic “skinning” functionality as well.  Via an xml file, you can provide all of the colors for the gradients, buttons, etc.

[Edit: I've updated it with a more recent shot....]