Some mp3 albums I have added have tile background imagery while the most are grey. So at least there can be tile graphics for music not bought in the app store. But why no imagery then for most artists when they are are well represented in the app store?
Take my Chet Baker mp3 album which I have copied from an old computer. No live tile graphic. Lock screen os grey as well. The app store has background images for his albums. Nokia Music for some reason has background music for this album but hardly anything else I have added. But no album icon for some reason.