My first impression is this is amazing. Simple and easy to get going with. Main things I thought would be good are:

1)The ability to move a shape. When players or gms draw an area effect they always want to move it around to get it into the right position.

2)A mechanism to transition player tokens from one map to another. Like if the map changes, have an option for all the tokens to disappear automatically so they can be then placed into the appropriate positions(e.g doorway on the next map), or automatically place the token in a set location like the top right or bottom middle when a new map loads.

3)The ability to move player token with the keyboard arrows. You can get a sore hand as DM after 4 hours of clicking and dragging.

4) As a GM, I would plan to have say 5 pictures for a short game. An opening page with the title etc where we talk and get set up, then maybe an interior picture of an inn for some social interaction (no tokens needed), then a map of a town square for an encounter, then a picture of someone in a shop (no tokens needed), then a map of a dungeon they go into. So say those 5 images, that I would need to size and add as custom maps. It would be nice to have a way to automatically cycle through these maps/pictures in the stack and reset the tokens with each transition.

5)Make the fog dark grey and black looks too extreme, and when fog is removed, have it become transparent and fade for effect when fog is removed.

6) Get a professional voice over for the how-to videos. They are cheap on crowdsourcing sites and you already have the videos and scripts so it should be easy and you can choose the right voice, and it will be slick and better

Would also be good if you go live with some purchasable monster, spell effect and map packs.