For the past two months or so I have been working on and off on a set of modular dungeon tiles (for roll20 and rpgnow), and I have learned a lot from it, and frankly I wish I could redo it. Attached is a quick example I threw together in about 15 or 20 minutes - but the point of this post is to call out to other creators of modular content and ask for some tips. I created one other modular set, but I didn't quite like it either - and is there a particular way to get tiles to mesh better?
I've also decided to work on a free set in the near future for practice, which I will also post here.

tl;dr I made a set of modular dungeon tiles, I don't like them and would like tips to improve them.
ExmapleModularDungeons.png
(This map is supposed to be an underground goblin fighting ring)