fluid engine Fluid Engine: css for border around image block

I'm using FE and cant find the CSS to add a border around an image block that uses a shape.

To add a border to an original image, I use the code below and make sure the image is in "fill" mode. You have to adjust/size the block to fit the image but it seems to work.

#block-yui_3_17_2_1_1668125166103_10204{
    border: 3px solid black;
}

But when I switch the square image to a round shape, the border stays square as you can see below. Im obviously missing something. Can anyone help?

Hi,

Can you share link to page in screenshot? We can check code easier