Pretty sure the profile page width is 616 pixels. If you make your images that width, it should center up. If you upload a PNG, then your image could be composed of the actual picture, and an ‘invisible’ layer that is 616 pixels wide. (I’ve never actually tried that, so it’s just a theory)
Also, If you’re doing search buttons in rows of 3, then make each one 205 pixels wide.
I’m sure there a more sophisticated code process I’m unaware of that would work better.