Hello @MIM !
You can get rid of the background by going to www.remove.bg.
To align the images in the thumbnails (right, left or centre) there should be an option when you upload the images - these options depend on which theme you are using.
Hope this helps!
I have already removed the background of the images and they are PNG files but shopify ads self different colors as background in relation to the colors in the images and I don't know why.
I use the pipeline theme and there are no options available for center the thumbnails when I upload them or in customize page. So I am looking for a code for this