You can easily mockup your web prototypes for high-resolution displays, commonly known as retina or high DPI.
InVision will display any image at 50%—it doesn’t matter if it's a screen or a background. All you have to do is use the modifier @2x (e.g. firstname.lastname@example.org) in your file name.
Please note that the @2x modifier is case-sensitive. Uploading files with @2X (an uppercase x) will not have any effect.
Use only when necessary, as full-page high-resolution images may double your prototype's loading time, which may result in worse performance on slower connections.
Learn more about InVision and @3x here.