If the current template folder does not include /images/infobox/top_left.png and top_right.png then looking at the product_info page the corner images of at least Cross Selling and Also Purchased boxes are wrong. This is likely to also apply to
infobox/top_left.png and infobox/top_right.png are not being found within the current template folder, and the /images/icons/default.png image is diplayed instead of using the fallback template images.
From a quick look at classes/boxes.php, this could be something to do with using DIR_WS_TEMPLATES in function contentBoxHeading, rather than doing something involving bts_select('images', 'infobox/top_right.png').
Create an empty template folder, switch to it. Enable Cross Sell Module and/or Also Purchased module for product_info pages. Look at a product page where one of these boxes applies.