You should create a marketplace something similar to [login to view URL]
This will be used for legal transactions.
There should be a possibility for a user to register either as a vendor (sellers account,have to pay a vendor bond ), or a buyer (normal account).
A vendor should be able to upload pictures and info to his items.
There should be an Escrow functionality.
The site should get an adjustable percentage of the finished deals.
There should be an admin panel for maintenance, resolving disputes and support.
There should be a Bitcoin handling mechanism.
It is recommended to run Bitcoind as the client only to connect to blockchain.info.
No blockchain download, no local wallet. 
There should be four types of access permissions
Administrator: Access to every part of the site.
Support: Access to read and reply to support tickets. Resolving disputes, only access to funds placed in escrow.
User: Access to own account only
Vendor: Access to create lists and sell products.
Vendor Level ranking system
Become a Vendor, and level up by the same math algorithm Alphabay is using
Categories Possibility to filter and sorting
There should be no captcha on the site. A user should instead be UNIX-like blocked from access after 5 failed login tries for 20 min.
All EXIF data should be removed from JPG's when uploaded to the site. 
The menu and sub-menu items
- Become a seller
- Withdraw to account
+ Possibility to filter
- Domestic -from- -to-
- Shopping cart
- Escrow mode
- New Orders
- Accept Orders
- Sent Orders
- Finished Orders
Private Messages (Encryption GPG)
- New message
- 2-FA GPG - Two-Factor GnuPG for Two-Factor?
- PIN For all user for withdrawing money any user create the pin FIRST TIME WHEN CREATE MEMBER
- Report a problem