SQL Server:use el parámetro en CREAR BASE DE DATOS

Tendrás que usar SQL dinámico

SELECT @sql = 'CREATE DATABASE TestDB ON PRIMARY ( NAME = ''TestDB_Data'', 
 FILENAME = ' + quotename(@DataFilePath) + ') LOG ON ( NAME = ''TestDB_Log'', 
FILENAME = ' + quotename(@LogFilePath) + ')'

EXEC (@sql)