Icon Set Measure = 
SWITCH (
    TRUE (),
    [% Change vs Prior Year]  < 0, "data:image/svg+xml;utf8, <svg xmlns='http://www.w3.org/2000/svg' x='0px' y='0px' width='100' height='100' viewBox='0 0 100 100'> <circle cx='50' cy='50' r='40'  stroke='purple' stroke-width='4' fill='purple' /> </svg>",
    [% Change vs Prior Year] < 0.4, "data:image/svg+xml;utf8, <svg xmlns='http://www.w3.org/2000/svg' x='0px' y='0px' width='100' height='100' viewBox='0 0 100 100'> <circle cx='50' cy='50' r='40' stroke='green' stroke-width='4' fill='yellow' />
</svg>",
    "https://i.gifer.com/4Ym4.gif"
   --  "https://i.gifer.com/Omjx.gif"
)