Hello, I volunteer with Fantasy Grounds College as 'MapHatter' or 'KrisfromGTW' and can vouch for what's been taught - I make official map modules for FG so I know first-hand these dimensions are useful: Maps = 2048x2048, jpeg, 1-2 megabytes max file size, 50-60 pixels per inch (square) Maps only

That said, it was Phergus, (if you are the one and same), who was the one to teach me that 1350x900 is the optimal size for map making in FG and less than 500kb as it retains the balance between minimal file size and maximum clarity. When you share a map or token in FG, for all your players to see it, you have to share the load for them too - thus if you share a map at a table with seven players, you are sharing it seven times and shouldering the payload which eats up your resources (approx 4g). The PHB uses 1.5g alone, so FGC teaches lots of tricks, through experts and programmers and a large range of other teachers and people in the know, that help reduce this footprint on resources, and map sizes and file types is one of the big ones. Tokens are another. So while you can use larger and dif file types like PNG, its not advised as it will slow and crash your system eventually. 1350x900 happens to be the exact number of pixels per square to mark out a 50px grid perfectly within FG. FG was built in such a way originally as to be a tabletop supplement you could consult at the table as a tool - but people came along that wanted it to be more, to be an actual playable tabletop like R20 - so over time they drastically modified things, and still make all kinds of extensions to improve its capabilities. Smiteworks caught on to the fact and have since been trying to develop a more powerful program that doesn't have these restrictions - but they never expected it to be used the way it was so a lot of work has to be done to change the way it was originally set up.