Serviio Album Art

Apologies if this has been answered before.

I have just switched to Serviio for streaming music - excellent programme!

However, album art shows up on nStream when accessing iTunes. However, any other folders with FLAC files do not show album art. I've tried naming the covers folder.jpg, cover.jpg etc. but nothing shows.

Am I doing something wrong?

I have a feeling I've missed something simple here.