The plugin doesn’t add any css or style, but a simple “text-align:center;” to the container DIV.
On other hand, theme style influences the card display, so sometimes a CSS correction is needed.
Unfortunately, different themes could have different settings, so there is no general solution.
The Images CSS class option of the Game page adds a CSS class to the DIV tag containing the card: e.g., if you created a CSS class for the card images named mycardimage, you enter mycardimage in the text-box of the option.