You can already do that with CSS 
Just target these classes and you can change the style of the grid however you like:
.google-photos-grid-thumbnail - the thumbnail images
.google-photos-codeblock - the embedded codeblock container
.google-photos-modal-grid - the popup modal grid container
I have updated v1.1.12 to show a message when there are no items found, and set the height of the block to fit that text content:
