Your podcast's artwork
The artwork of your podcast will always be your profile picture on SoundCloud.
If you want to submit your RSS feed to iTunes, you must make sure that your profile image’s artwork is at least 1400x1400 pixels, and no larger than 3000x3000 pixels.
If your artwork is not between these image requirements, you will receive an error from iTunes that says “Podcast cover art must be at least 1400 X 1400 pixel JPG or PNG, in RGB color space, and hosted on a server that allows HTTP head requests”.
After you've updated your profile picture, you can run your RSS feed through Podbase https://podba.se/validate/ to validate if it meets iTunes requirements or not.
Checking your artwork's pixel dimensions
Find the file size and pixel dimension of a file from a saved file on your computer, or through your RSS feed.
Saved file on your computer
If you have the image saved on your computer, you can find out the pixel dimensions through the image’s information.
On a Mac: Open the image file in Preview. Click on Tools in the top menu and select Show Inspector. A pop-up window will open, and under the title ‘Image size’ you will see the pixel height and width of your image.
On a PC: Right click on the image file, look at Properties, and then the Summary tab.
Your RSS feed
If you are unsure what dimensions your artwork is, go to your RSS feed (Available through your Content Settings page) and copy-paste the link within the <itunes:image>.
From there, open up your console, and scroll over the img style tag to view the pixel dimensions of your artwork.
Submitting your podcast to iTunes
You can then submit the podcast to iTunes' Podcasts Connect portal to refresh your feed. Just go to http://podcastsconnect.apple.com/ and click your podcast to see details, then click “Refresh”. This triggers the iTunes Store to re-check your feed.
Please allow up to 24 hours for the podcast to be updated on iTunes.