I noticed that alot of people asked about places for their custom things. Because of this i started to make a list of Cool places where you can make malls/events/instances. In this post Ill just post 6 places (i already have like 22 but don´t have enough info to all of them).
These are the places I will show you today:
1. Dun Morogh Special Place
2. Area next to Wetlands
3. Stormwind Vault
4. Ironforge Airport
5. Old Ironforge
6. Grim Batol
I will use some different colors so i will explain them here:
Pink - Notes
Orange - History
Green - Pro
Red - Contra
1. Dun Morogh Instance
.worldport 0 -5582.658691 887.209534 392.631073
Notes: This area is really cool. It is very large and has cool features
like a ring of molten snow where you could place a fire boss or whatever :P
There are other good features: It is not like a round place. You can spawn at one point and you
have to fight till you get to the end.
Pro:
- large area
- cool features (texture etc.)
- great place for an instance
Contra:
- Only Contra i can think of is: Horde can go to IF easy.
But I think thats no big problem 
Pic: Pic

2. Area next to Wetlands
.worldport 0 -3438.822510 -3644.946289 56.700352
Notes: This is an area where you can make obstacle courses.
Its just a big flat area. An instance wouldn´t
be that good there because there is no change anywhere.
Just big, flat nothing :P
Pro: -Big Area
Contra: -Kinda boring :/
Pic: Pic

3. Stormwind Vault
.worldport 0 -8653.801758 607.536316 90.675499 / .recall port StormwindVaultEntrance
Notes: I think everyone knows this.
This is like the Stormwind Stockades (The Stormwind Instance)
but its built different. It is good for an instance (come on blizz built it
)
Instance History: The Defias found a big red jewel.
This is an artifact that was made by Neltharion, the Aspect of Earth.
Now the best mage of the Defias stole the artifact and got incredible power
(you know as always in this storys). Your part is to kill him, destroy the crystal
and try not to blow whole Stormwind up.
Pro:
-Built by Blizzard
-Complete Instance
-Lots of places for bosses (I mean special places)
Contra: -
Pic:Pic

4. Ironforge Airport
.worldport 0 -4653.808105 -1688.603882 503.324615
Notes: There are plenty guides on this site how to reach this airport
so i recommend making a mall (or an event) here. You can do alot of things there.
Pro:
-Buildings (great for a mall)
-Ironforge Guards (if you make an Allicane mall there)
-little troll fight that you could script 
-Scripted Npcs (ok just emotions but who cares)
-large area
Contra:
-Horde can go to IF easily
-Ironforge Guards (if you make a neutral or Horde mall there)
-some mobs
Pic:Pic

5.Old Ironforge
.worldport 0 -4815.6 -1033.32 438.683
Notes: Im shure alot of you know about Old Ironforge.
Old Ironforge is the old town of Ironforge (SUPRISE!!!)
and it was opened due the alpha of WoW.
Today it is closed but there are ways to get in there (look here on mmowned.com)
This place is a big lair. In it there are giant jewels and ofc lava
. Just look into there
yourself. I recommend this for a mall.
Pro: -fully textured
-Cool place to hang out
Contra:
-Sometimes the King of Ironforge gets bugged and attacks the Horde through the walls
Pic: Pic

6.Grim Batol
.worldport 0 -4070.542725 -3456.188232 281.388184 / .recall port GrimBatol
Notes: An AWESOME place for an instance.
Delete those dragon mobs nobody needs and you can make an street instance.
Cool Textures are included and you have to fight from gate to gate to finaly reach
the entrance of Grim Batol. (ok its closed but...)
You could use the place infront of the entrance as a mall too but i HIGHLY recommend
this area as an instance.
Instance History: The historians of the dwarves have new founds of Grim Batol.
Grim Batol was a big city of the dwarves like Ironforge. But before a long time
the connection of the two cities was interrupted.
The scouters of Ironforge that were send there never came back. Now it is controled by red dragons.
Go to the entrance of Grim Batol and try to find some more information!
For the real story of Grim Batol go here: Grim Batol - WoWWiki - Your guide to the World of Warcraft
Pro: -Awesome place
-Fights between Gates - run from gate to gate to get to the entrance of Grim Batol
-Some gameobjects
-war enviroment (destroyed vehicles, burning things, etc.)
Contra:
- Mobs already exist there.
- End of the instance would be easily to reach from Loch Modan -> Invisible Walls requiered.
Pic: Pic

If there are any problems with the thread send me a pm or just reply on the thread. This is just the first part of a line of those threads.
Ok pic tags dont work-.- I will add them manually Sorry for that