"In his pride and arrogancy, with a reckless feeling of security Belshazzar “made a great feast to a thousand of his lords, and drank wine before the thousand.” All the attractions that wealth and power could command, added splendor to the scene. Beautiful women with their enchantments were among the guests in attendance at the royal banquet. Men of genius and education were there. Princes and statesmen drank wine like water and reveled under its maddening influence. PK 523.2"
"Belshazzar the king made a great feast to a thousand of his lords, and drank wine before the thousand."
EGW directly quotes Daniel 5:1 and elaborates on the scene described in the verse. This is a clear and direct allusion.
"Woe unto them that rise up early in the morning, that they may follow strong drink; that continue until night, till wine inflame them! And the harp, and the viol, the tabret, and pipe, and wine, are in their feasts: but they regard not the work of the Lord, neither consider the operation of his hands."
Both passages describe excessive drinking and revelry. While EGW doesn't directly quote Isaiah 5:11-12, the description of Belshazzar's feast echoes the themes of drunkenness and disregard for God found in Isaiah.
"With reason dethroned through shameless intoxication, and with lower impulses and passions now in the ascendancy, the king himself took the lead in the riotous orgy. As the feast progressed, he “commanded to bring the golden and silver vessels which ... Nebuchadnezzar had taken out of the temple which was in Jerusalem; that the king, and his princes, his wives, and his concubines, might drink therein.” The king would prove that nothing was too sacred for his hands to handle. “They brought the golden vessels; ... and the king, and his princes, his wives, and his concubines, drank in them. They drank wine, and praised the gods of gold, and of silver, of brass, of iron, of wood, and of stone.” PK 523.3"
"Belshazzar, whiles he tasted the wine, commanded to bring the golden and silver vessels which his father Nebuchadnezzar had taken out of the temple which was in Jerusalem; that the king, and his princes, his wives, and his concubines, might drink therein. Then they brought the golden vessels that were taken out of the temple of the house of God which was at Jerusalem; and the king, and his princes, his wives, and his concubines, drank in them. They drank wine, and praised the gods of gold, and of silver, of brass, of iron, of wood, and of stone."
EGW directly quotes and paraphrases Daniel 5:2-4, making this a clear and explicit allusion.