As the pillar created is decided by your mark rather than the card, perhaps a generic pillar-under-construction would be better than the base pillar for the element in question?
I'm good with whatever the artist wants to do within the bounds of a pillar and a burst of energy.
My original vision in my head was of just the base of a Pillar with nothing on top of it yet representing where you will use your mark to create the new pillar and the burst matching the 3 quanta the spell gives you.
Bloodshadow said that he thought the art would look nicer if we used the Base pillar for the element that the burst produces, ie and Entropy pillar for Entropic rush. I don't really think it makes as much sense as my visionary picture but if it looks good and isn't directly confusing then i'd go with it. I understand that sometimes art doesn't make sense.