On our development site (just accessable via host file change) we have the following issue: When clicking a filter, the images of K2, embedded in the k2 template override not as img but as CSS background-image disappear.

Here is the k2 category_item.php code:
<div class="itemImage" style="background-image: url(<?php echo $this->item->image; ?>)"><a class="projectlink" href="<?php echo $this->item->link; ?>" title="<?php if(!empty($this->item->image_caption)) echo K2HelperUtilities::cleanHtml($this->item->image_caption); else echo K2HelperUtilities::cleanHtml($this->item->title); ?>">
<img class="cattrans" src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg==" alt="<?php if(!empty($this->item->image_caption)) echo K2HelperUtilities::cleanHtml($this->item->image_caption); else echo K2HelperUtilities::cleanHtml($this->item->title); ?>"/>
</a></div>

After filtering, the css attribute background-image is empty in the frontend.
Without filtering, everything works normal in K2.
Any advise?

Dear spotteron,
Please you go here www.smartaddons.com/support/tickets, submit a ticket.
Best Regards