Currently, images you place on the VTT space, like maps or tokens, don't render at full resolution when the zoom's changed. This is most noticeable if you have a large map or other image file and change the zoom level, causing the entire image to render at a lower resolution and become blurrier. It happens with all files as far as I can tell, but the higher-resolution the image is, the more noticeable the blur gets. I think it'd be nice to have a toggleable option to force images to render at full resolution even when zoomed (at a cost of the end user's resources/performance), especially when dealing with regional or atlas-style maps that might have particularly small text or icons.