Store Commander supports .png image format for all PrestaShop versions.
You will find 2 settings options under Tools > Settings > Images
If you enable the use of PNG format, existing images will not be taken into consideration. You will need to upload them again.
Please note that .png file extension can sometimes not be recognized by your store.
To resolve this display problem:
Verify the .htaccess to ensure that rules related to the .png images URL rewriting do exist. If this is not the case, you will need to duplicate all information related to .jpg rule and replace it by .png.
You will then need to modify the store's template to add the .png extension.
Use method 1 in Store Commander's settings to keep the .jpg extension.