If you set the map size to 48 pixels per grid and stay at 100% zoom, do things look OK? There are always going to be compromises on a system that allows users to zoom in and out of a graphic, and the graphic you upload is not really the graphic you see. Roll20 converts every uploaded graphic into 4 different sizes, for efficient display at varying zoom levels (similar to how Google Maps displays tiles at different zoom levels). There are some ways you can mitigate this. Does your map mapping program export as jpg, png or gif? The last of these has some serious limitations for re-sizing and zooming. You could see if you get better display by converting before uploading. If your map is designed to emulate 8bit graphics, you may be out of luck. Those are designed for single resolution, and no zooming. You will have quality issues in that case. Finally, can you upload a screenshot showing the quality issues? And for those who might be familiar with it, what map making program are you using? Again, there may be users with specific experience and workflows who can lend a hand.