Pixellu SmartAlbums 2 - The fastest, easiest and most intuitive album design software available.
Photopea - Online photo editor, which can work with PSD, XCF and Sketch files (Photoshop, Gimp and Sketch App).
Moments Designer - Moments is a complete album design package aimed for both professional and amateur photographers.
Replace Cover - Create beautiful cover art for your Spotify playlists
Fundy Designer - A Professional Suite for Professional Photographers.
Headers.me - Create social cover images that get you followers