All of my map tiles are importing as squares. Why?

I have a bunch of good images from Imperial Assault map tiles I want to use for a campaign.  The dimensions range from 462x627 to 2052x1965 and I don't think as single one is perfectly square.   When I import them to my library and then drag them to the map, they come out square.  E.g., the image for tile 02B is a 1300x1887 jpg.  When I drag it from my library, it comes in at 200x200. However, if I delete it from my library and simply drag it from Windows File Explorer onto the map so that it is imported and placed on the map in one step, it comes in at 1061 x 1540 -- the proper aspect ratio. If I delete that tile form my Roll20 map and then drag the very same image that was *just* imported from my library to my map, it once again gets placed on the map in square 200x200 dimensions. What am I doing wrong?

Are you on the Token Layer, or Map Layer? I've found in my experience that dropping things on the Map Layer will leave it in the original dimensions while the Token Layer usually crunches it down to a square.

On the map layer.