The Droste Style was set to Spikey Spiral to produce this picture.  It was based upon a photo of tree branches taken in my back yard.  Some of the branches crossed each other to form a roughly diamond shaped area near the center, and that region was made transparent by using the GIMP graphics program.  The Droste Tool uses the transparent area to determine which parts of the image should be replicated and where.  With a 'normal' Droste effect (see below), the recursions wind into the transparent portion.  The Spikey Spiral essentially unwinds the framed area and coils it into distant nothingness.

The picture below was made from the same source image, but with the Droste Style set to Winding Boxes, creating a more traditional looking Droste effect.  And here's a more colorful version of the above Spiral Droste.