I would like to think that the engine itself is advancedAre there currently some "advanced" features to this engine? Such as allowing background pictures in say... listboxes, or treeviews or even the editor gadget?

But to answer your question, listboxes, treeviews, and editor gadgets are not yet supported... They will be supported in future updates... All gadgets that are currently supported do have many 'advanced' features. They support basicly every WS_ style you can think of... that goes for text alignment as well as things like images on buttons... The engine is designed to clone all features of XP skinning...
Currently Supported Controls:
- Buttons (including ToggleButtons)
- ImageButtons
- Checkboxes
- Radio Buttons
- GroupBoxes (Frame3D)
- Static Text (TextGadget)
- Static Images(ImageGadget)
- TabControls (PanelGadget)
- HeaderControls (Top portion of a ListIcon Gadget)
- Windows (client area only)
- Limited ToolBar support (Background is controled by the parent window's BG)
- Window (borders/regions)
- ListViews
- ListIcons
- TreeViews
- Edit Controls
- ProgressBars
- ScrollBars
- Menus
- UpDown (SpinGadgets)
- ComboBoxes
Animated controls are not supported w/ XP skins, therefore they won't be supported here... Transparency might be trick on win95/98, so we'll have to see about that. We do, however, have plans to impliment transition effects (such as 'fade') and possibly sound effects later on...How about animated or gradiant or custom titlebars? Ability to have a level of transparent windows? I already have the code for that but wanted to know if it'll be a native feature to the engine..
Not at the moment. In the future we are going to move to a zip-based skin format so that you will have the ability to easily add in more files...Is it possible to extend the skin file itself?
We've gotten a lot of requests for a lib version and we are strongly considering it for a later release...If there will be two versions or a key version or whatever, would it be possible for you to provide a PB LIB version at an extra cost? Still including credits etc..