Dear Victoria,
I also have exactly the same problem with the grid row. Do you guys have a solution already? It seems that whenever you insert an image as a cell background you have to choose the right attachment display settings. Only then I get high resolution pictures. For example if you choose medium 300 x 200 and select scale to fit or stretch to fit the image becomes pixalated. It should be better to choose a custom width.
But i hope you guys have found a better solution then I came up with.
Regards,
Orville