I was wondering if it was possible to put a image instead of this blank billboard
Take a look here: http://www.facepunch.com/showthread.php?t=769903
Thx but where is Entity shared.lua ?
In the given example the author used a scripted entity to draw a billboard in 3D2D. A scripted entity is usually defined by lua files named init.lua, shared.lua and/or cl_init.lua.