Alright the best site by far (I think) to get custom items, vendors, etc. is WoW Vendetta - Wage Your War You need to be registered now I believe so sign up first.
Okay first off, press tools, you can go to any of these following links from them:
Weapon Creator
Armor Creator
Jewelry Creator
Bag Creator
Ammo Creator
Vendor Creator
And lastly they have a model viewer.
Okay first off I'll start with how Weapon Creator works, most of them work the same way but I'll explain how to use each of them. NOTE: I just post new things on other topics, if it has the same thing as the other topic above it, like Armor Creator and Weapon Creator, it's in Weapon Creator, if that makes sense.
Weapon Creator: First pick the name for your weapon. Next pick the quality, poor, normal, uncommon, rare, epic, legendary, and lastly artifact. Next you want the quote such as "This blade is as fierce as a tiger" it's the yellow text at the bottom of items. The display ID is what the item looks like, and also the item ID, the Item ID you can put any random number in as long as it's not taken. The display ID, go to Wowhead: It's all about elegance. and look at weapons, when you see one you like, look the weapon up in your database and find the display ID, write that down where it should go. Next is the "equip, it means how it sheaths the weapon, or puts it away. The type is what kind of weapon it is, ie. two hand axe. Repair either has it be weapon/shield or unrepairable, if you choose unrepairable once it breaks your screwed. Durability is how much damage your weapon can take, the bigger the durability the longer it can stay unbroken. "Binds" is if it's Bind on Equip, Bind on Pickup, etc. Item Requirements means what level you need to be to equip it. Item level you can put what ever you want, it really doesn't matter much. Max number allowed, like unique (3) is how many maximum you can have of that item. Allowable class is what class can use the weapon. Stackable does not mean YES OR NO, it means how many can stack, if none leave blank. Damage minimum, and maximum, doesn't matter, you can leave some blank and fill in others, and change their attack type between fire,ice,arcane,holy,physical,nature or shadow. Stat types are what stat bonus it gives, then just fill in next to it how much it should bonus. Item Resists, what the resistants are from the item and for what type of damage. Item bonuses, like +110 strength automaticly on the item. Item sockets, what sockets can be used. Item value is for if you are going to have it vendored, you can enter in a set price.
Armor Creator: Material basicly means what it's made out of, ex. plate armor. Repair, you can change it to cloth for it's less expensive or put on plate for most expensive. Block is if it's a shield, how well it blocks. Armor is how much armor it has to protect you.
Jewelry Creator: Equip Ring, Necklace, Trinket, which one of those is it.
Bag Creator: Slots, how big the bag is ie. 36, that's the inventory slots.
Ammo Creator: Ammo Type, is it gun bow or crossbow?
Vendor Creator: Subtitle means what is under it's name like if it's general goods "General Goods" would appear under it's name. Vendor ID is basiclly like weapon ID etc. Level, what level is it. Faction means what faction it belongs to, like Stormwind, or Darnassus, or Orgrimmar. Health+Mana how much health or mana it has. Mount Display, what mount does it have? If none leave blank. Vendor ID again matches the ID that you put before. Item ID, what item is being sold from the vendor. Quantity, how many does the vendor have? If unlimited leave blank.
After you finish making whatever you're making, press if you want mangos or antrix, Then just find the ascent, or antrix one under antrix tab, Press download batch, save it where you'll remember it, then go onto whatever database program your using, and execute batch file, find the file and presto you just completed whatever you were working on!
Credits go to me, yay me! Please no flaming, if you do not understand something please respond and ask.