Size: Apple Music recommends a minimum size of at least 4000 x 4000 pixels in size.
Format: JPG, PNG, or GIF format.
Density: Use 72-300 dpi for cover art.
Aspect Ratio: Maintain a square aspect ratio for best results.
File Size: Keep your file size under 10 MB.
Apple Music also recommends the following guidelines:
No misleading or generic cover art (for example, prominently depicting or referencing an artist who does not perform on the album).
Only include relevant information such as artist name, release title as text, and the exact song title or album as released.
No blurry, pixelated, tilted, or cropped images unless intended.
No additional information (including social media handles, email, website, logos, or any other reference to competitors of Apple Music and the iTunes Store).