Consider examining shopping mall layouts when mapping dungeons - their looping design is perfect for creating diverse environments that are interesting to navigate.
Include social encounters & challenges in a dungeon, especially if inhabited by wandering humanoid creatures.
Dungeon Generators
DNGEN - A one-click dungeon concept generator created by Karl Druid for MorkBorg. It’s system neutral and can be use for grimdark fantasy dungeons in any setting.
One Page Dungeon - A one-click one-page dungeon map generator. Tends towards a classic fantasy flavor. Includes a dungeon name, description, and rooms. Can be paired with DNGEN for creating dark fantasy dungeons.