Large Maps

So I am mapping out a large dwarven hold and am loathe to break it up into dozens of small (25x25) maps. My question is if i were to make the map in gimp or photoshop and port it into roll20 would that ease the loading of a large map (200x200 or more). From all i know it should but want to be positive.

The dynamic lighting will have much more to do with performance than the map size. I routinely have maps that are 100x100 or 200x200. 

Thank you for taking the time to reply. Do you use DL or fog of war on the larger maps

All Dynamic Lighting. No Fog of War or Advanced Fog of War.  And to be clear, I don’t notice much, if any, lag on my system. I have had players with weaker computers that experienced some issues. Mainly on large open maps with lots of small obstructions. The one I’m thinking of was a massive forest split by a deep gorge. I put in about 20 pseudo-random marks for each tree to make the forest have shifting sight lines and really feel forest-like. On maps that were massive sprawling caverns and corridors, I probably had just as much complexity but rarely very open visibility, and those maps all seemed fine for the same group of players. 

the problem i am encountering is my pc is high end and suffer no issues but i have a player in greece and one in poland on a laptop and the internet service isnt great so i am trying to soften the blow so they can enjoy the game. I prefer building in roll20 but if building the maps in gimp or photoshop lessen the impact then i am adept at both and would go that route if it would do anything. 

It certainly won’t hurt to make it in an external program. I haven’t found one yet that is as intuitive as Roll20’s interface, but there are some decent options. 

I agree thanx for the assistance, always a pleasure Aaron.