Dyson Logos's G+ account is an endlessly scrolling inventory of hand-drawn D&D maps, each one cooler than the last.
Logos accompanies his maps with detailed notes about his inspirations, creative process, and the games that result from them. A separate site lets you see the adventures that accompany the maps.
He runs a Patreon, where patrons can fund his ongoing work and free releases of his maps for commercial and noncommercial work.
Crypts and Sewers: "While the left hand set of catacombs is rougher and is used exclusively for the burial of the deceased, the structures in the right-side catacombs are much better maintained and involve a lot of heavy masonry work – implying that the church above uses it for more than just a burial site (in fact, assuming that most of the doors are locked, it would appear that they bury very few people down here, having only a few crypts directly attached to their chambers and passages)."
The City of Letath: "The first of these cities to get finished is Letath, a small coastal city that the party travelled to and then left within 20 minutes of game play. Basically enough time for me to throw down the map on the table and then fast forward through them negotiating a fair place to teach the young chiefling they were escorting, and then to head north to their true destination of Winterspire."
Dyson's Maps & Cartography [Dyson Logos]