To create this Kaleider Masking example, a photo of a pretty rose was first loaded.  Then the Set Background/Create Negative Stencil option was performed to both set that picture as the Mask Background, and also use it as the basis to automatically create a 'negative' Stencil.  That caused the rose blossom and other light areas to become static, while the darker portions behind it could be changed.  A photo with contrasting, subdued colors was then loaded, and one of the Side Wedge Diamond Mirror Patterns was rendered (I forget which one).  The Scale slider was used to adjust the Tile size so the pattern fit nicely without dominating the rose.
Kaleider Rose Mask