What size is the egg?
If large enough, it could be a darning egg. Or it could be art glass, as you say.
The blue and whites are a mixture. Many appear to be modern marbles -- Vacor. But some look vintage. The ones with the brightest white swirls are the ones most likely to be Vacor.
Looks like a lot of vintage West Virginia swirls in the red and whites.
Maybe a Master after that.
The greens are a mixture, some patches, some swirls, different makers. Maybe Akro on the largest one.