All podcast platforms have their own conditions when it comes to artwork. These change on a a regular basis. To make sure you meet the standard requirements, here's an ideal file format for podcast artwork:
Extension: .png or .jpg
Size: 3000 x 3000 pixels
You can use different artwork for your show and each of your episodes. Make sure you upload the right file. If you want to know more about artwork, check out our article about podcast artwork.