Welcome, Valerie.
Wow, your Alien Mantis and other digital abstract bugs are unique! I was JUST having a conversation with my husband about how to be "different". Those definitely standout; haven't seen anything like them in my 5 months here.
Abbie is right; I didn't know that aspect ratio made a difference when I started to upload images. Yet their program does a pretty good job in sizing to fit, with a few exceptions. I just go in to Edit Image (at bottom of picture) after the upload, to make any custom minor placement adjustments under Customize Product; hit Submit, and it shows my preference over the computers preference. :-)
Really enjoy your bold and energetic colors and designs!