Just for fun
I had a somewhat symmetrical shot of two mountains, so I thought I'd blend them. I didn't do any projection, just a slight translation in the y axis.
I had images of watches that I thought would be interesting to blend. I didn't do any warping on the two watches, though. You can see the ghosting effect because of this.
Feather Blending
Pyramid Blending
Feather Blending
Gradient Blending