The closest thing to Snapchat for Windows Phone 8 is anUnofficial app on the Windows store that isn’t functioning right yet.  I read the reviews for it and there are way too many complaints.  Below is the link to the unofficial Snapchat app.

Rumour: Snapchat waiting for GDR3 before coming to Windows Phone

snapchat windows phone 8 rumor http://www.windowsphone.com/en-us/store/app/snapchat-unofficial/5131e4b3-14b6-4d91-bdd6-2fb8d022a215

Snapchat (Unofficial)

snapchat windows phone 8    

The first Snapchat app for Windows Phone! Take quick snaps with your phone and send them to your friends!