Am I seriously overloading your servers?

I'm making a simple map foundation where every map tile is the same image. Whenever I try to cut and paste, and move around, 40+ tiles at once, the server connection is severed. The last map troubles, I solved by pasteing, reloading, pasteing, reloading... I can understand how my own browser struggles with re-displaying 40-100 images, causing lag, but I don't get why the connection would suffer a complete breakdown because of it. Shouldn't it just lag too? (I use Firefox, and I already tried clearing the browser cache.)

Did you group the tiles together and convert it to a drawing first? That apparently removes a lot of extra information that isn't needed on a per tile basis for background stuff.

I can group them together and convert them to a drawing? Wow! I'll try that later. However, that conversion would probably take place after me placing all the tiles. I just held LMB down and drew across the area to copy, to mark multiple tiles, pressed Ctrl-C, then placed the cursor where I wanted a copy, and pressed Ctrl-V. It is immediately after pasting the tiles, that the connection crashes. It doesn't immediately say it does, but that's by judging from where the campaign restores.

Honestly... roll20 isn't that great for building a complex map. You would be better off using gimp, photoshop, or even maptool to create your maps and then import them as a single image into Roll20.

Maybe, but I figured building a map out of small assets, would keep the storage use down. Instead of a huge image for every map, I have a library of many tiny images for all maps.