...your own void. Also a mark/recall/warp-to-void spell. All in one? Certainly, just select what you wish to do when you cast it. What's the significance of this void, realm, plane of oblivion, or whatever you wish to call it? It can be a home to your summonable creatures and you can place your valuables here.

Ideas for the void itself.
-Perhaps your void needs to have an encumbrance so you don't exploit this. Quantity instead of weight? 5,10, 20, or maybe even up to 50 items/monsters can be kept within the void?
-Furniture? A bed?
-A window showing wherever you would recall when you wish to leave.

So, you probably see why you would want a temporarily/permanent place to keep your possessions in an emergency, but why would your summonable creatures live here? Well, it's so they can become stronger. It's so they belong to you and only you. These companions conjured from oblivion, summoned from the afterlife, or reanimated into zombies, can become stronger and stronger the more you use them. I they die, they're gone and to start over you must conjure a new one.
Going beyond all this, now we have an opportunity to summon whatever we wish by capturing creatures.

Ideas for capturing creatures
-After trapping a soul in a soul gem, release the soul into the void.
-This can work for black souls as well. When released you will see a ghost of the npc you captured. (This is lore friendly.

Spoiler

The ghost of Rufio and Lucien can be summoned in Oblivion and Skyrim)

-After conjuring a monster, you can trap them into a soul gem so you may release them into the void.
-Or better yet, simply conjure a thrall when in the void.

Ideas for rules on what you can summon from the void
Just an FYI: The way I see it, conjured monsters come in three forms: daedra, spirit, and undead. daedra are conjured from oblivion, spirits can be either trapped and bound or conjured, and undead are corpses reanimated via magic. Skeletons and dead thralls are very much the same.
-Any monsters you conjure, including reanimated corpses, can live here.
-Spirits only (You can only release souls you've captured in soul gems into the void as it's a spirit realm)
-Conjured monsters only (no companions or reanimated corpses)
-Undead only (it's strictly necromancy)
-Companions only (followers/npcs and reanimated corpses)

Sounds like it could go somewhere, if it were more lore friendly. But my question is, why would you Conjure from your own real when you can just Conjure from Oblivion? Unless you can upgrade and customize your minions, it seems a tad pointless.

Cutting into the void of oblivion to make your own realm would require more time and power then you're character realisticly has. They do have access to
a key ingredient already during the course of events, A Sigil Stone, but that would only allow you to open a portal to the realm it came from, Dagons.
Not sure why anyone would want to splice off a part of Dagon's realm, I imagine that would not go well.

But Conjuration could really use a boost like fixing the scaleing of what you can resurrect with necromancy, increase the power level of
atronaches, depending on your conjuration level. A level 30 conjurer summons the exact same fire atronach a level 100 master does.

Uh, I'll avoid the Void. Do not want to piss off Sithis..

Though nice idea, would not mind seeing a mod for it.

Read the book On Oblivion. A true master of conjuration has the power. Also... As I said, you probably see why you would want a temporarily/permanent place to keep your possessions in an emergency, but why would your summonable creatures live here? Well, it's so they can become stronger. I'm not sure how much you can customize a flame daedra, but any ideas would be great. I suppose you could give your pet items like rings or amulets.

Haha! I beat you to it.

http://www.gamesas.com/topic/1320212-what-new-spells-would-you-like-to-see/page__fromsearch__1

May not be the same, but still.

how about the ability to telepathicly speak to deadra you bind (not liket he norma summoning, like the unbound dremora you have to summon and convince to do what you tell it). your idea is silly though, it would take a team of master mages to create a realm in oblivion and sheogorath only knows what could happen when you actually go there, legions of deadra could actually invade since the realm is in oblivion, princes could show up and do whatever they want to you, very powerful mages who are seeking the knowledge of oblivion could stumble in and try to kill you because they were just in the mad house, lots of things could go wrong

Nice

I agree with voice of reason that it would be incredibly dangerous attempting to maintain a realm of oblivion. It would indeed make sense if an entire guild or guilds (the Psiijic?) to take on such a task without intruders. Perhaps the power that protects Urn from being constantly attacked can be applied to this void? Nothing like this has ever been done before, so technically it's all up in the air.