Hm what do you mean without using any polygon controls?
You can create a WriteableBitmap, and draw on it with any tools you prefer. If you want to avoid all additional tools you can call set/get pixel methods and for loops.
When you are happy with your WriteableBitmap you can create a BitmapImageSource and then call .AsBitmap() on your WriteableBitmap. With that complete you can then use the whole imaging SDK chain.
Edit: You can find the .AsBitmap method in Nokia.InteropServices.WindowsRuntime namespace.