Hello hkharris -
We are not aware of any issues that would cause images to appear distorted when enlarged on a listing page.
It is possible that, if your uploaded images are smaller than the supersize window that they become enlarged to suit the window and if they are sufficiently small, this could cause some pixelation of the image when supersized.
We typically recommend using images 1280 x 1024 - 1920 x 1440 px.
If the issue persists, please let us know a few sample items where this is occurring in a support case so we can take a look into it.