Hey! I'm glad it's helpful :)
No such feature now, you'd have to import the image again. I want to add a similar feature, but it isn't there yet.
I have more dice shapes planned, yeah, but very little time for development. I hate to say this, but for fancy potion-shaped dice you'd probably be better off finding some STLs or building them from scratch in Blender. I might add such die shape in the future, but this app won't be able to compete with an actual 3d-modelling software when it comes to complex, custom geometries.