Closrapexa - good question! I am hoping someone knowledgable with the Thoth will jump in and give us some info.
IMO I personally see this as like the energy / fire is bursting forth from within the wand - like it is the creative energy that comes from within.
I have also read somewhere (cannot remember where at the moment) that sometimes Mages of old would use hollow wands or usually staffs that they would fill with something (liquid, smoke, solid) to give the wands / staffs more power or energy or connection to themselves.
Looking forward to some more feedback on this card.
CreativeFire
PS. Keep these questions coming as they are also inspiring me to look at different things in the cards / images that I have only just begun to notice.