I know that Astral Spells are like support spells to make the main schools stronger, but I believe it would be a pretty cool idea if there were Astral spells that actually attacked themselves. Like having a Star Magic spell as a collapsing star turn into a black hole and is and AOE attack. Or possibly a Moon Magic spell that is called Lunar Glow that heals a person for a certain amount of health. It could work like how Shadow Morphs were first introduced where certain schools could get a certain morph. ~Sorry if this is already a topic~
While it would be cool to see, damage isn't the purpose of the Astral Schools. Their purpose is to enhance our own spells or to change it up completely (moon). Also, another good reason why we wouldn't want Astral damage spells is because they are notoriously difficult to build resistance against, and to shield because Astral resistance is a combination of other resists. Only Tower, Legion, and any form of shield that absorbs damage can defend against it. There is a reason why storm's Insane Bolt has a chance of hitting yourself for 10,000 damage, or hitting the enemy for 1,000 Moon Damage; it's difficult to defend against.
Now regarding the Shadow School damage spells, we have those already in the form of Dark Nova, Dark Fiend, and Dark Shepherd. I guess you could argue they are Shadow Creatures, but they can deal damage, and that damage is also hard to defend against for the same reasons Astral schools are.
attack spells as well would be cool, but cooler then 
but they would all be cool.