Vector rendering doesn’t display raster images. If you want vector linework and raster textures you must use Hybrid. You can set the Display and Output Resolution to High if you need to see better quality than you get with Medium. Keep in mind that setting Display Resolution to High will make your graphics card work harder and may result in lagging as you are working on your project.
This is the difference I see between Medium and High OutPut Resolution on my machine. In both cases I’ve enlarged the PDF to 400% which is a little extreme. Click on the images to see them full sized.
And - what you see on screen might look not so nice if you have the quality set to low, but have high quality set for export… I do 80% of my work in Raster, and use the overide to Hybrid on export for the remainder of the work.