As discussed in this thread, there is currently no API available that would allow to let WRT widgets use the currently set skin and wallpaper.
There is however a way to perfectly fake this. The idea is to create two static images (one for landscape and one for portrait mode). These two images are then used in the widget as background images (defined via CSS). Note that those images will not be transparent, instead they look as if they were .
I've used this technique in my ComingNext HS widget. Here is a sample:
Now the difficult part is to create those two images. There is no WRT API to get the current wallpaper, neither is there a way to access the current skin graphics. However, this quite easy using a native C++ API. So I've created an application that will do just that: create two images using the current skin and wallpaper. You can give it a try here: ComingNext Skin Fetcher v1.0. The sourcecode is also available under the GPLv3 here.
Now to put this to the next level, an integration into ApiBridge would be awesome, so that we could use the functionality from within WRT widgets without the need for a separate application. Are there any information available on how to write ECOM plugins for use with ApiBridge? Anyone interested in helping developing on this?