From the wiki (I've highlighted the size limits, but am including the full text in case either of you hasn't tried both upload methods): There are two methods for uploading art to Roll20. The first way is to click and drag a single image from your file explorer/computer to the Tabletop and it will upload as well as place the graphic where you designated on the Tabletop. The second way is to click on the Upload button underneath My Library . This pops open a dialog box called Upload Files... . This dialog box has a dashed-border rectangle where you can drag a maximum batch of ten images at a time to upload them all at once. You can also select images one at a time with the Choose a file... button which brings up a file selection menu to browse for files on your computer/device. There is a file size cap for image uploads. If you have a base account, no single image or batch upload can exceed 5MB. For Plus or Pro subscribers, this cap is raised to 10MB.
