Working with Marketplace purchased maps

Is there a way to download and edit purchased maps outside of Roll20? I have Gabriel's excellent Small Town 2 River map collection. The party is at the bridge river crossing map. Some of the buildings have second stories, which he created a separate map for. Rather than having to switch back and forth between separate pages set up for downstairs / upstairs (not to mention a battle running over into both areas at once!), I would like to take just an image of the 2nd floor of the building the party is closest to and lay that down somewhere on my existing map. WAY more convenient that way in terms of actual play. Essentially, I want to take the map he created, go into GIMP/Photoshop, select the 2nd floor of a building, extract it and save it as a PNG with a transparent background, then upload that PNG in My Library so I can drop it onto our current map page. Can I do this in Roll20? Or am I S.O.L.?

You can go to the marketplace and any set you purchased in there that isn't exclusive (none of mine are) will have a download complete set option.  For multi level maps you can also lay the stories next to each other on you Vtt (this is what I usually do) so you don't have to go between pages.  There isn't anything preventing you from using more than one map on a single page and Jpg will burden the system a lot less.  In the rare event you don't have much else on the map layer you can just move it to the back of the image stack of the map layer bringing up the next floor.   Not sure if either of those solutions are ideal for your particular vision though.  Good luck!

Ah! I was looking in My Library, didn't realize that I had to go back to the Marketplace to download. Thanks! I was indeed worried about burdening the system and lag from putting multiple intensive graphics down. Maybe the jpg maps are less of a burden than I thought.