The Android Play Music app seems to randomly, arbitrarily decide to not show album art.
It is annoying me. A lot.
What I usually do is to save the cover in a file called "albumart.png" using The Gimp in the folder holding the Ogg Vorbis-files I use to store music on my phone.
Sometimes Play Music picks it up, sometimes it doesn't. Seemingly at random.
The latest pattern I have observed is that it helps if the images is 500x500 pixels rather than 1000x1000 pixels, and it helps if the image is embedded in the first .ogg file in the folder.
Sometimes it is not necessary to embed the image.
If the image is "large", say 1000x1000 pixels, then embedding it in the .ogg file makes Play Music not recognize the Title and Artist tags in the file.
It is an incredible mess.
Is the source code available somewhere?