Add thumnail image to search results dropdown

I've made some progress with search and have moved on to what appears in the dropdown for the search bar in the header. I note that by default I get 

.sqs-search-preview-ui.no-image .sqs-main-image-container {
display: none;
}

but if I override display:none I get a blank 50x50 box which gets filled with nothing. I have  no idea what is going on but it seems to be pointing at the correct image. Can anyone enlighten me or provide a solution to getting the product image to appear next to the product title in the results

TIA

Debbie