You can use tabber, see https://wow.gamepedia.com/index.php?title=Template:WC3UnitBox&action=edit for example.
Somehow, I think that I am doing something incorrectly. I had tried changing this template instead of the book one hyperlinked to above, but it definitely did not work.
You can insert the below wiki-text into your preferred infobox. However, if you're having trouble implementing the code, I can do it for you if requested.
| colspan="2" style="text-align: center;" | {{#if:{{{image2|}}}| {{#tag:tabber| Front Cover = [[File:{{{image}}}|100px]] {{!}}-{{!}} Back Cover = [[File:{{{image2}}}|100px]] }} | {{#if: {{{image|}}} | [[File:{{{image}}}|100px]] | }} }}
Once this is done successfully, you can use CSS to customize the display of the tabber tabs.