I added an image to my sidebar the other day but was bothered by it not being centred. SO i went on the hunt and found a very simple solution!
Add an Image module to your sidebar or footer and then add your image.
Then click on the image module again, and you’ll see this screen:
You’ll see in the image that I’ve added the text “aligncenter” in the Image CSS Class box. Doing this will now centre your image.
Click Update, and then click Save.
Now check your site, and your image module will now be centred!