Where can I find a ton of Silver enemies?
Once you complete the game once, all but three Lynels on the world map will become Silver Lynels. (The three remaining Lynels are one of each colour (Red, Blue and White) to allow you to get the pictures).
A lot of enemies within Hyrule Castle are silver tier. A Silver Moblin and 2 Silver Lizalfos can be found in the Training Room. More silver Moblins can be found throughout the castle.