Try using a bit less liquid and you'll avoid the glycerin rivers, if you wish. There are times they add a great deal to a soap though.
Usually people use a tall and skinny mold for the butterfly swirl because you get more length for the wings. I think it's harder to get the look in a loaf mold, but it can work.
What are you using for your swirl tool? This technique seems to work best if the soap is at a medium trace, where it's like a soft pudding, so a thin swirl tool won't move the soap much but will cut through it. From my own limited experience and seeing what other people use, something the thickness of a gear tie, a McDonald's straw, or a 1/4 dowel works pretty well. It's tough to get just right.
They make cool designs but I have the same thoughts as some of the others. Most people look at, use, or sell a single bar of soap so the effect of the butterfly is fleeting, I suppose just as a real butterfly can be.
I hope you don't mind some constructive feedback. I was looking again and I see most of the swirls you did in the middle of the soap. To get the wing effect, the pattern I have seen consistently is to start with your swirl tool going right down the wall where you have poured most of the colors and then looping out and back to the wall. I'll try to find a visual.
Here are two visuals for the two different patterns and of course you can make your own up, but the commonality is they they go down the "color wall" and then loop back through it and come up that side as well to finish. Hope that helps!