You probably came here looking for Tripcode Explorer.
Or perhaps you came looking for Tidus, official mascot of desktop threads. Gallery here.
A desktop thread is a forum (aka discussion board) thread in which participants post pictures of their desktop. Sometimes it is under the guise of expecting comments or ratings. In actuality, it is simply to show off what little there is to show off about a desktop.
For trolling, it is common post with desktop backgrounds that they hope will have their originals requested. They then proceed to ignore those requests.
You can use the following for assistance:
There is an IRC channel at Rizon #desktopthread
There is an experimental, low activity image board here.