I spent a little time today playing with the TexGen code today and ended up adding two new texture mutators - Twist and Warp. As you might imagine, Twist will cause the image to twist around a given point on the plane, accomplishing this by rotating requested image positions around the center point by an amount that is dependent on the distance from that center point. The other mutator, Warp, will cause a localized expansion or contraction of the image, accomplishing this by scaling requested image positions by an amount that is dependent on the distance from the requested point of the warp.