I have been using Conky to display the current track information from Amarok. This uses qdbus, the command qdbus org.kde.amarok /Player GetMetadata gives a great deal of information on the track including lyrics, artist, title etc. and the cover art. Search for amarok conky script and you will find lots of examples using this method. It was the cover art that gave me problems recently.
I haven’t used Amarok for a while as I tend to switch between Clementine and Amarok. When I started Amarok conky would show the track details but for many tracks it wouldn’t display the cover art even though it was displayed in Amarok. I searched for a while until I found the problem.
Looking at the output of the qdbus command I saw that sometimes the ‘arturl’ was a file in the music directory. This is where I have put covers that I downloaded manually or that came with the album. I would then use Amarok’s set custom cover screen so Amarok would display them. These lines in the qdbus output show illegal characters like ‘%’ that weren’t part of the filename. When it was a cover that Amarok had downloaded automatically it would be listed as a file in ~/.kde/share/.apps/amarok/. These files worked in Conky.
The answer was simple but time consuming. I used Amarok’s fetch cover option which would then display the custom cover I had previously set. I select it and then it works in Conky. There may be a better way but I haven’t found it yet. Hopefully I will only need to do it for one track from each album.