Hello Luke,
thanks for downloading MH Magazine lite.
What do you mean with “shape” of the images? The size?
You can find all image sizes of thumbnails in the file functions.php as for example:
add_image_size('cp_small', 70, 53, true);
That’s the size of the small thumbnails for the MH Custom Posts widget.
Change it as you like. Here you can find more information: https://codex.www.ads-software.com/Function_Reference/add_image_size
After you have changed the sizes, you will have to regenerate your thumbnails, otherwise you won’t see any effects: https://www.mhthemes.com/blog/how-to-regenerate-thumbnails-after-a-theme-change/
Regards
Michael