Thank you!
Will Woodgate sells the RefinedSlider stack that incorporates several effects, and they are, in fact, random. You don’t have to pick just one for your slideshow. Every image carries its own transition effect. It also has a decent thumbnail presentation. An older stack by some other developer, RefinedSlidr, was terrible with thumbnails, if you had more than 5-6 images in your slideshow. The thumbs were so small, they were unreadable, plus they were spaced out far from each other.
I am not sure what the cost of these effects was to Will, but to me, that was an affordable stack. of course, it lacks the full functionality I am looking for. 