Press the green flag. Press 1 for HD. (vector) Press 2 for less HD. (bitmap)
How to get a high quality image in Scratch: 1. Get a vector art editor other than Scratch. (such as Inkscape - free) 2. Open your HD image in it. 3. If it isn't already, resize the image to the correct resolution. (Like if you import a 1920*1080 pixels image and it isn't that when you import it then resize it to 1920*1080 pixels) 4. Save it as .svg. 5. Open in Scratch and resize if needed.