You say the file icon is pixellated - but is the image file itself still of the quality that you expect to see?
Hopefully, you will discover how to attach your images so we can see what you have.
If you drag your PSE file into a folder, does the file icon show differently there? Make sure that the View Options are set to show icon previews.
If you open that file in Quick Look, does the image appear properly? (Just click on the file to select, and press your space bar for a Quick Look view)