These Tiles have an extremly high resolution of 1200dpi. Tiles included in the Quests have only 300dpi resolution to reduce file size.
Under "Requirements" in the Quest Pages you can see which and how many Tiles you need.

HeroQuest and Expansions:

Advanced HeroQuest and Expansions:

DragonStrike:

HeroQuest A Marvel Winter Special:

Games Workshop Dungeon Rooms:

Games Workshop Dungeon Lairs:

Games Workshop Caverns Dungeon Floor Plans:

Warhammer Quest:

Others: