As a long-time user of VTT as well, I definitely agree here. Maps for VTT benefit from not having the grids on them. Just make the map align to a certain dimension* and then say what it is. The user then sets up the map to that size and then is done. This allows the user to operate without a grid, use a different grid color, or add their own terrain objects without disrupting the grid.
*For the dimensions, setting out the dpi and making sure the map dimensions are a multiple of that makes it much easier for a user. A 32x20 map at 100 dpi that is 3200x2000 pixels is super easy to use and handles zooming in fairly well. The user drops the image onto a 32x20 space in the VTT and is done.
EDIT: And the art style is lovely too. Makes me think of Wakfu.