Shapeshifting. Required by gods who want to shrink down to a merely mortal size and interact with others. Also necessary for gods who want to assume a demonic form that better fits their personality. Polymorphing others would probably fall under this too, but would be harder.
Flesh-weaving for gods who want to create new species or otherwise alter folks.
Portals for gods who want to open paths between realms and such.
Metamagic for general mana manipulation, gathering and merging with mana sources.
Emotions/minds for mind-affecting stuff. Illusions might be lumped under here.
Natural Order for making harsh, barren areas lush with life (and weather control, which is generally needed to keep that life going).
The traditional 4 elements, just because. And it allows us to support elemental PCs. They might be called different stuff, though, like Storm, Ocean, Stone and Inferno.
Possibly Unmaking for a Void-style disintegration/weakening art.
Some sort of scrying/divination art? Or should that just be subsumed into the others, so that each one can scry for stuff in their specialty, but there isn't a "pure" divination-for-everything art?
Energy fields for TK and mage-lock and creating similar effects.