If you want to publish an app and don’t have a lot of money to spend on an icon, you can use the sips (scriptable image processing system) command to resize an image and use it as an icon. Find a creative commons licensed image. Let’s say your app has something to do with money or finance. Search for an image that you can use. Download the image and save as xxxxx.png
Open the terminal app and run the sips command:
"sips --resampleWidth 57 xxxxx.png --out Icon.png"
Run the same command again, but this time change 57 to 114 for the retina display and output to Icon@2x.png instead.
"sips --resampleWidth 114 xxxxx.png --out Icon@2x.png"
You can now use these in xCode as icons for your app.