If you uninstall TwistedBrush your artwork remains on your computer. All artwork that you create in TwistedBrush is stored in folders under the main TwistedBrush folder. These folders are labeled Book1, Book2, Book3 etc and correspond to the books within TwistedBrush. Files for each page are stored within these folders, including the .TBR file, which is the TwistedBrush image format. A BMP file for each page is also included so you have a file version that can be loaded into virtually any other Windows art program.

Also see this topic: Where are my images (pages and books) stored on Windows Vista and Windows 7?