I never got the square picture to work for me the other day, when I swapped the files round it loaded up on the artist page but would not open any of the boxes on the home screen, then when i quit roon and re-started it, roon advised my database was broken, even though reverted back to the original file that had been replaced which was odd.
I think will stick with the circles for now as in the process of sorting my artist photos out by adding better quality ones than the default ones that are there.