Do you mean the embroidering on the corners look too low-res? If that's the case, try this:
(I'll be using the above image to demonstrate)
In the FileSystem (bottom left on the image), select the image you used in your Sprite node. Once you have selected, go to the "Scene" tab (top left on the image). Right next to the "Scene" tab should be the "Import" tab.
Once you are in the Import tab, it should look like the above.
Note the file selected in the "FileSystem" and the "Reimport" button.
Once you are here, you should try fiddling around with the properties. Try to turn "filter" on and off. To apply the changes, press "reimport". If you turn filter off (and it doesn't work), turn it on again and turn on "mipmaps".
(I'm also assuming the image you are working with is a Raster image (.PNG, .JPG), and not a vector image.)
And also a few more things to note from my own experiences:
If your images are low-res, of lower quality, or they are too small, well then you should find yourself a better image.
If your images are vector images (and they are .SVG format), try scaling the vector image in the "SVG" section.
And finally, if your images are too big (so if they are too big, or you scaled them up too much in the SVG section), as soon as you down-scale the big image, it will turn pixelated and weird. If this is the case, turn on 'filter' and 'mipmaps'.
For further reading: