I have idea about a new achievements in the beta 1:
"Strange room" - You need to enter the secret room in floor 1.
You are so rich! - You need to have 9999 baldi bucks.
Achievements master - You need to have all achievements in the game.
The end? - You need to complete the story mode.
Random madness - You need to complete all levels from Random mode.
The map - You need to buy the minimap.