The picture file, however, must be no more than 90 pixels in either direction.
How do you ensure that? Funny you should ask... :lol:
Open the picture you want to use with "Paint". In Windows Wxplorr, that involves right clicking on the file, hovering over "Open with ...", then selecting paint.
Now, click on Resize. That will bring up a box by which you can describe the resize.
Click on the Pixels radio button. Select whichever of the Horizontal or Vertical values is larger and set it to 90.
Save As ... the picture, so you don't mess up your original. I usually simply add an "a" for avatar onto the end of the original name.
This picture will now load just fine.